H 


UNIVERSITY  OF  CALIFORNIA 
AT   LOS  ANGELES 


LO$  A,, 


PROFESSOR  JOHN  TYNDALL'S  WORKS. 


Essay*  on  the  Floating  Matter  of  the  Air.  in  Relation 

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New  York :  D.  APPLETON  &  Co.,  1,  8,  &  5  Bond  St. 


FRAGMENTS    OF   SCIENCE: 

A   SERIES  OF  DETACHED   ESSAYS,   ADDRESSES 
AND   REVIEWS. 


BY 

JOHN    TYNDALL,   F.B.8. 


FIFTH  EDITION. 


NEW    YORK: 
D.    APPLETON    AND     COMPANY, 

1,    3,    AND    6    BOND     STREET. 
1884. 


/ 


PEEFACE 

TO 

NEW     EDITION. 


IX  VIEW  of  the  present  edition  of  these  '  Fragments,* 
I  have  carefully  re-examined,  recast,  and  to  some  ex- 
tent remodelled  them,  adding   some  new  ones    to  those 
published  in  former  editions. 

In  regard  to  style  they  are  as  clear  and  simple  as 
I  could  make  them.  In  regard  to  matter  my  desire  has 
been  that  they  should  utter  nothing  base. 

JOHN  TTKDALL. 

ATHENXUM  CLUB:   March  24,  1876. 


PEEFACE 

TO 

THE    FIRST    EDITION. 


MY  MOTIVE  in  writing  these  papers  was  mainly  that 
which  prompted  the  publication  of  my  Eoyal  Insti- 
tution lectures  ;  a  desire,  namely,  to  extend  sympathy  for 
science  beyond  the  limits  of  the  scientific  public. 

I  have  carefully  looked  over  all  the  articles  here 
printed,  added  a  little,  omitted  a  little — in  fact,  tried  as 
far  as  my  time  permitted  to  render  the  work  presentable. 
Most  of  the  essays  are  of  a  purely  scientific  character ;  and 
from  those  which  are  not,  I  have  endeavoured,  without 
veiling  my  convictions,  to  exclude  every  word  that  could 
cause  needless  irritation. 

From  America  came  the  impulse  which  induced  me  to 
gather  these  '  Fragments '  together,  and  to  my  friends  in 
the  United  States  I  dedicate  them. 

JOHN  TYNDALL. 

ATHENKUM  CLUB:  March  1871. 


CONTENTS. 


MM 

TKB  OPTICAL  CONDITION  OF  THE  ATMOSPHERE,  IN  ITS  BEAR- 
INGS ON  PUTREFACTION  AND  INFECTION         .  .  [1  to  [36 

PAET  I. 

I.    THE  CONSTITUTION  OF  NATURE.     1865  .        .  .  .3 

II.     RADIATION.     1865  .  .  .  .  .      .      27 

III.  ON  RADIANT    HEAT    IN    RELATION    TO    THE    COLOUR    AND 

CHEMICAL  CONSTITUTION  OF  BODIES.     1866         .  .71 

IV.  NEW  CHEMICAL  REACTIONS  PRODUCED  BY  LIGHT  .       .       93 
V.     ON  DUST  AND  DISEASE.     1870            .             .             .  .126 

VI.  VOYAGE  TO  ALGERIA  TO  OBSERVE  THE  ECLIPSE.     1870  .  .     186 

VII.  NIAGARA.     1872                       .            .            .            .  .218 

VIII.  LIFE  AKD  LETTERS  OF  FARADAY.     1870  .            .            .  246 

IX.  THE  COPLEY  MEDALIST  OF  1870         .            .            .  .268 

X.  THE  COPLEY  MEDALIST  OF  1871  .             .             .  .     274 


x  CONTEXTS. 

PAQK 

XL     ELKMBNTAUY  MAGNETISM        .  •  •  •  .284 

XII.    DEATH  BY  LIGHTNING       .  .  •  •  .      .    309 

XIIL      SCIKNCH  AND   THE   'SPIBITS'  «  •  •      SI* 


PART  II. 

IHTRODUCTTOK,  EMBRACING  EEFLECTIONS  ON  MATERIALISM  .  325 

L    REFLECTIONS  ON  PRAYER  AND  NATCRAL  LAW    .            .  .  357 

II.    MIRACLES  AND  SPECIAL  PROVIDENCES.     1867              .  .  379 

HI.    SCIENTIFIC  MATERIALISM.     1808          "     .             .             .  .  409 

SIV.    SCIENTIFIC  USB  OF  THE  IMAGINATION.     1870             »  .  423 

V.    VITALITY.     1865  .            .            .            .                        .  .  459 

VI.    ON  PRAYER  AS  A  FORM  OF  PHYSICAL  ENERGY.     1872  .  466 
VIL     THK  BELFAST  ADDRESS.     1874.             .             .            ..472 

APOLOGY  FOB  THE  BELFAST  ADDBESS              .            .  .  638 

VIII.    CRYSTALS  AND  MOWSCULAR  FORCE.     1874           .            .  564 

LETTER  FROM  THB  '  TIMES'  OF  NOVKMBKR  9,  1874  .  .  583 


THE  OPTICAL  CONDITION  OF  THE  ATMOSPHERE, 
IN  ITS  BEARINGS  ON  PUTREFACTION  AND  IN- 
FECTIONS 

AN  enquiry  into  the  decomposition  of  vapours  by  light, 
begun  in  1868  and  continued  in  1869,  in  which  it 
was  necessary  to  employ  optically  pure  air,  led  me  to  ex- 
periment on  the  floating  matter  of  the  atmosphere.  A 
brief  section  of  a  paper  published  in  the  '  Philosophical 
Transactions '  for  1870  is  devoted  to  this  subject. 

I  at  that  time  found  that  London  air,  which  is 
always  thick  with  motes,  and  also  with  matter  too  fine 
to  be  described  as  motes,  alter  it  had  been  filtered  by 
passing  it  through  densely  packed  cotton-wool,  or  calcined 
by  passing  it  through  a  red-hot  platinum  tube  containing 
a  bundle  of  red-hot  platinum  wires,  or  by  carefully  lead- 
ing it  over  the  top  of  a  spirit-lamp  flame,  showed,  when 
examined  by  a  concentrated  luminous  beam,  no  trace 
of  mechanically  suspended  matter.  The  particular  por- 
tion of  space  occupied  by  such  a  beam  was  not  to  be  dis- 
tinguished from  adjacent  space. 

The  purely  gaseous  portion  of  our  atmosphere  was 
thus  shown  to  be  incompetent  to  scatter  light. 

1  I  have  held  back  the  publication  of  this  edition  of  the  '  Fragments,' 
BO  as  to  embrace  among  them  some  account  of  this  investigation.  The 
previous  completion  of  the  rest  of  the  volume  has  rendered  the  separate 
paging  of  this  chapter  necessary. 


2]  FRAGMENTS   OF   SCIENCE. 

I  subsequently  found  that,  to  render  the  air  thus 
optically  pure,  it  was  only  necessary  to  leave  it  to  itself 
for  a  sufficient  time  in  a  closed  chamber,  or  in  a  suitably 
closed  vessel.  The  floating  matter  gradually  attached 
itself  to  the  surrounding  surfaces,  leaving  behind  it  air 
possessing  no  scattering  power.  Sent  through  such  air, 
the  most  concentrated  beam  failed  to  render  its  track 
visible. 

The  parallelism  of  these  results  with  those  obtained 
in  the  excellent  researches  of  Schwann,  Schroeder  and 
Dusch,  Schroeder  himself,  and  of  the  illustrious  Pasteur, 
in  regard  to  the  question  of  '  spontaneous  generation,' 
caused  me  to  conclude  that  the  power  of  scattering  light 
and  the  power  of  producing  life  by  the  air  would  be  found 
to  go  hand-in-hand. 

This  conclusion  was  strengthened  by  an  experiment 
easily  made  and  of  high  significance  in  relation  to  this 
question.  It  had  been  pointed  out  by  Professor  Lister, 
of  Edinburgh,  that  air  which  has  passed  through  the 
lungs  is  known  to  have  lost  its  power  of  causing  putre- 
faction. Such  air  may  mix  freely  with  the  blood  without 
risk  of  mischief;  and  that  truly  great  scientific  surgeon 
had  the  penetration  to  ascribe  this  immunity  from  danger 
to  the  filtering  power  of  the  lungs.  Prior  to  my  becom- 
ing acquainted  with  this  hypothesis  in  1869, 1  had  virtually 
demonstrated  its  accuracy  in  the  following  way : 

Condensing  in  a  dark  room,  and  in  dusty  air,  a  power- 
ful beam  of  light,  and  breathing  through  a  glass  tube 
(the  tube  actually  employed  was  a  lamp  glass,  rendered 
warm  in  a  flame  to  prevent  precipitation)  across  the  focus, 
a  diminution  of  the  scattered  light  was  first  observed. 
But  towards  the  end  of  the  expiration  the  white  track 
of  the  beam  was  broken  by  a  perfectly  black  gap,  the 
blackness  being  due  to  the  total  absence  from  the  ex- 
pired air  of  any  matter  competent  to  scatter  li^ht.  The 


PUTKEFACTION   AND    INFECTION.  [3 

deeper  portions  of  the  lungs  were  thus  proved  to  be  filled 
with  optically  pure  air,  which,  as  such,  had  no  power  to 
generate  the  organisms  essential  to  the  process  of  putre- 
faction.1 

I  thought  this  simple  method  of  examination  could 
not  fail  to  be  of  use  to  workers  in  this  entangled  field. 
They  had  hitherto  proceeded  less  by  sight  than  by  in- 
sight, being  in  general  unable  to  see  the  physical  charac- 
ter of  the  medium  in  which  their  experiments  were  con- 
ducted. But  the  method  has  not  been  much  turned  to 
account ;  and  this  year,  while  preparing  these  'Fragments' 
for  publication,  I  was  so  impressed  by  its  possible  import- 
ance, that  I  resolved  to  devote  some  time  to  the  more 
complete  demonstration  of  its  utility. 

My  principal  stimulus,  however,  was  the  desire  to  free 
my  mind,  and,  if  possible,  the  minds  of  others,  from  the 
uncertainty  and  confusion  which  now  beset  the  doctrine 
of  '  spontaneous  generation.'  Pasteur  has  pronounced 
it  a  'chimera,'  and  expressed  the  undoubting  con- 
viction that,  this  being  so,  it  is  possible  to  remove 
parasitic  diseases  from  the  earth.  To  the  medical  pro- 
fession, therefore,  and  through  them  to  humanity  at  large, 
this  question  is  one  of  the  last  importance.  But  the  state 
of  medical  opinion  regarding  it  is  not  satisfactory.  In  a 
recent  number  of  the  '  British  Medical  Journal,'  and 
in  answer  to  the  question,  '  In  what  way  is  contagium 
generated  and  communicated  ?  '  Messrs.  Braidwood  and 

1  '  No  putrefaction,'  says  Cohn,  '  can  occur  in  a  nitrogenous  substance 
if  it  be  kept  free  from  the  entrance  of  new  Bacteria  after  those  which  it 
may  contain  have  been  destroyed.  Putrefaction  begins  as  soon  as  Bacteria, 
even  in  the  smallest  numbers,  are  accidentally  or  purposely  introduced.  It 
progresses  in  direct  proportion  to  the  multiplication  of  the  Bacteria  ;  it  is 
retarded  when  tho  Bacteria  (for  example,  by  a  low  temperature)  develop 
a  small  amount  of  vitality,  and  is  brought  to  an  end  by  all  influences  which 
either  stop  the  development  of  the  Bacteria  or  kill  them.  All  bactericidal 
tnedia  are  therefore  antiseptic  and  disinfecting.' — Beitragezur  Biologic  der 
Pfianzen.  Zweites  Heft,  1872,  p.  203. 


4]  FRAGMENTS  OF  SCIENCE. 

Vacher  reply  that,  notwithstanding  'an  almost  incalcu- 
lable amount  of  patient  labour,  the  actual  results  obtained, 
especially  as  regards  the  manner  of  generation  of  con- 
tagium,  have  been  most  disappointing.  Observers  are 
even  yet  at  variance  whether  these  minute  particles,  whose 
discovery  we  have  just  noticed,  and  other  disease  germs, 
are  always  produced  from  like  bodies  previously  existing, 
or  whether  they  do  not,  under  certain  favourable  condi- 
tions, spring  into  existence  de  novo.' 

With  a  view  to  the  possible  diminution  of  the  uncer- 
tainty thus  described,  I  have  recently  submitted  to  the 
Royal  Society,  and  more  especially  to  those  who  study  the 
^Etiology  of  disease,  a  description  of  the  mode  of  pro- 
cedure followed  in  this  enquiry,  and  the  results  to  which 
it  has  led. 

A  number  of  chambers,  or  cases,  were  constructed, 
each  with  a  glass  front,  its  top,  bottom,  back,  and  sides 
being  of  wood.  At  the  back  is  a  little  door  which  opens 
and  closes  on  hin'ges,  while  into  the  sides  are  inserted  two 
panes  of  glass,  facing  each  other.  The  top  is  perforated 
in  the  middle  by  a  hole  2  inches  in  diameter,  closed  air- 
tight by  a  sheet  of  india-rubber.  This  sheet  is  pierced  in 
the  middle  by  a  pin,  and  through  the  pin-hole  is  passed 
the  shank  of  a  long  pipette  ending  above  in  a  small 
funnel.  A  circular  tin  collar,  2  inches  in  diameter  and 
1£  inch  deep,  surrounds  the  pipette,  the  space  between 
both  being  packed  with  cotton-wool  moistened  by  gly- 
cerine. Thus  the  pipette,  in  moving  up  and  down,  is  not 
only  firmly  clasped  by  the  india-rubber,  but  it  also  passes 
through  a  stuffing-box  of  sticky  cotton-wool.  The  width 
of  the  aperture  closed  by  the  india-rubber  secures  the 
free  lateral  play  of  the  lower  end  of  the  pipette.  Into 
two  other  smaller  apertures  in  the  top  of  the  chamber  are 
inserted,  air-tight,  the  open  ends  of  two  narrow  tubes, 
intended  to  connect  the  interior  space  with  the  atmo- 


PUTREFACTION   AND    INFECTION.  [6 

sphere.  The  tubes  are  bent  several  times  up  and  down,  so 
as  to  intercept  and  retain  the  particles  carried  by  such 
feeble  currents  as  changes  of  temperature  might  cause  to 
set  in  between  the  outer  and  the  inner  air. 

The  bottom  of  the  box  is  pierced,  sometimes  with  two 
rows,  sometimes  with  a  single  row  of  apertures,  in  which 
are  fixed,  air-tight,  large  test-tubes,  intended  to  contain 
the  liquid  to  be  exposed  to  the  action  of  the  moteless  air. 
The  cases  have  varied  in  capacity  from  1,666  to  451 
cubic  inches. 

On  September  10  the  first  case  of  this  kind  was 
closed.  The  passage  of  a  concentrated  beam  across  it 
through  its  two  side  windows  then  showed  the  air  within 
it  to  be  laden  with  floating  matter.  On  the- 13th  it  was 
again  examined.  Before  the  beam  entered,  and  after  it 
quitted  the  case,  its  track  was  vivid  in  the  air,  but  within 
the  case  it  vanished.  Three  days  of  quiet  sufficed  to 
cause  all  the  floating  matter  to  be  deposited  on  the  top, 
sides,  and  bottom,  where  it  was  retained  by  a  coating  of 
glycerine,  with  which  the  interior  surface  of  the  case  had 
been  purposely  varnished.  The  test-tubes  wei'e  then 
filled  through  the  pipette,  boiled  for  five  minutes  in  a 
bath  of  brine  or  oil,  and  abandoned  to  the  action  of  the 
moteless  air.  During  dilution  aqueous  vapour  rose  from 
the  liquid  into  the  chamber,  where  it  was  for  the  most 
part  condensed,  the  uncondensed  portion  escaping,  at  a 
low  temperature,  through  the  bent  tubes  at  the  top. 
Before  the  brine  was  removed  little  stoppers  of  cotton- 
wool were  inserted  in  the  bent  tubes,  lest  the  entrance  of 
the  air  into  the  cooling  chamber  should  at  first  be  for- 
cible enough  to  carry  motes  along  with  it.  As  soon, 
however,  as  the  ambient  temperature  was  assumed  by 
the  air  within  the  case  the  cotton-wool  stoppers  were 
removed. 

We  have  here  the   oxygen,  nitrogen,  carbonic  acid, 


6]  FRAGMENTS   OP    SCIENCE. 

ammonia,  aqueous  vapour,  and  all  the  other  gaseous 
matters  which  mingle  morn  or  less  with  the  air  of  a  great 
city.  We  have  them,  moreover,  « untortured  '  by  calci- 
nation and  unchanged  even  by  filtration  or  manipulation 
of  any  kind.  The  question  now  before  us  is,  Can  air  thus 
retaining  all  its  gaseous  mixtures,  but  self-cleansed  from 
mechanically  suspended  matter,  produce  putrefaction  in 
organic  infusions  freely  exposed  to  its  action  ?  To  this 
question  both  the  animal  and  vegetable  worlds  return  a 
decided  negative. 

Among  vegetables  experiments  have  been  made  with 
hay,  turnips,  tea,  coffee,  hops,  repeated  in  various  ways 
with  both  acid  and  alkaline  infusions.  Among  animal 
substances  are  to  be  mentioned  many  experiments  with 
urine ;  while  beef,  mntton,  hare,  rabbit,  kidney,  liver, 
fowl,  pheasant,  grouse,  haddock,  sole,  salmon,  cod,  turbot, 
mullet,  herring,  whiting,  eel,  oyster  have  been  all  subjected 
to  experiment. 

The  result  is  that  infusions  of  these  substances  exposed 
to  the  common  air  of  the  Koyal  Institution  laboratory, 
maintained  at  a  temperature  of  from  60°  to  70°  P'ahr.,  all 
fell  into  putrefaction  in  the  course  of  from  two  to  four 
days.  No  matter  where  the  infusions  were  placed,  they 
were  infallibly  smitten  in  the  end.  The  number  of  the 
tubes  containing  infusions  was  multiplied  till  it  reached 
six  hundred,  but  not  one  ol  them  escaped  infection. 

In  no  single  instance,  on  the  other  hand,  did  the  air, 
which  had  been  proved  moteless  by  the  searching  beam, 
even  when  raised  to  over  90°,  manifest  the  least  power  of 
producing  Bacterial  life  or  the  associated  phenomena  of 
putrefaction.  The  power  of  developing  such  life  in  atmo- 
spheric air,  and  the  power  of  scattering  light,  are  thus 
proved  to  be  indissolubly  united. 

The  sole  condition  necessary  to  cause  these  long- 
dormant  infusions  to  swarm  with  active  life  is  the  access  of 


PUTREFACTION   AND    INFECTION.  [7 

the  floating  matter  of  the  air.  After  having  remained 
for  four  months  as  pellucid  as  distilled  water,  the  opening 
of  the  back-door  of  the  protecting  case  and  the  consequent 
admission  of  the  mote-laden  air,  sufficed  in  three  days  to 
render  the  infusions  putrid  and  full  of  life. 

That  such  life  arises  from  mechanically  suspended 
particles  is  thus  reduced  to  ocular  demonstration. 

Let  us  enquire  a  little  more  closely  into  the  character 
of  the  particles  which  produce  the  life.  Pour  Eau  de 
Cologne  into  water  :  a  white  precipitate  renders  the  liquid 
milky.  Or,  imitating  Briicke,  dissolve  clean  gum  mastic 
in  alcohol,  and  drop  it  into  water;  the  mastic  is  pre- 
cipitated, and  milkiness  produced.  If  the  solution  be 
very  strong  the  mastic  separates  in  cvirds;  but  by 
gradually  diluting  the  alcoholic  solution  we  finally  reach 
a  point  where  the  milkiness  disappears,  the  liquid  assum- 
ing, by  reflected  light,  a  bright  cerulean  hue.  It  is,  in 
point  of  fact,  the  colour  of  the  sky,  and  is  due  to  a 
similar  cause,  namely,  the  scattering  of  light  by  particles, 
small  in  comparison  to  the  size  of  the  waves  of  light. 

When  this  liquid  is  examined  by  the  highest  micro- 
scopic power  it  seems  as  uniform  as  distilled  water.  The 
mastic  particles,  though  innumerable,  entirely  elude  the 
microscope.  At  right  angles  to  a  luminous  beam  passing 
among  the  particles  they  discharge  perfectly  polarised 
light.  The  optical  deportment  of  the  floating  matter  of 
the  air  proves  it  to  be  composed  in  part  of  particles  of 
this  excessively  minute  character.  When  the  track  of  a 
parallel  beam  in  dusty  air  is  looked  at  horizontally 
through  a  Nicol's  prism,  in  a  direction  perpendicular  to 
the  beam,  the  longer  diagonal  of  the  prism  being  vertical, 
a  considerable  portion  of  the  light  from  the  finer  matter 
is  extinguished.  The  coarser  motes,  on  the  other  hand, 
flash  out  with  greater  force,  because  of  the  increased 
darkness  of  the  space  around  them.  It  is,  I  hold,  among 


g]  FRAGMENTS   OF   SCIENCE. 

the  finest  ultra-microscopic  particles  that  the  niattei 
potential  as  regards  the  development  of  Bacterial  life  is 
to  be  sought. 

Now  the  existence  of  these  particles,  foreign  to  the 
atmosphere  but  floating  in  it,  is  as  certain  as  if  they  could 
be  felt  between  the  fingers  or  seen  by  the  naked  eye. 
Supposing  them  to  augment  in  magnitude  until  they 
come,  not  only  within  range  of  the  microscope,  but  within 
range  of  the  unaided  senses.  Let  it  be  assumed  that  our 
knowledge  of  them  under  these  circumstances  remains  as 
defective  as  it  is  now — that  we  do  not  know  whether  they 
are  germs,  particles  of  dead  organic  dust,  or  particles  of 
mineral  matter.  Suppose  a  vessel  (say  a  flowei'-pot)  to 
be  at  hand  filled  with  nutritious  earth,  with  which  we 
mix  our  unknown  particles ;  and  that  in  forty-eight  hours 
subsequently  buds  and  blades  of  well-defined  cresses  and 
grasses  appear  above  the  soil.  Suppose  the  experiment 
when  repeated  over  and  over  again  to  yield  the  same  un- 
varying result.  What  would  be  our  conclusion  ?  Should 
we  regard  those  living  plants  as  the  products  of  dead  dust 
or  mineral  particles,  or  should  we  regard  them  as  the  off- 
spring of  living  seeds  ?  The  reply  is  unavoidable.  We 
should  undoubtedly  consider  the  experiment  with  the 
flower-pot  as  clearing  up  our  pre-existing  ignorance ;  we 
should  regard  the  fact  of  their  producing  cresses  and 
grasses  as  proof  positive  that  the  particles  sown  in  the 
earth  of  the  pot  were  the  seeds  of  the  plants  which  have 
grown  from  them.  It  would  be  simply  monstrous  to 
conclude  that  they  had  been  <  spontaneously  generated.' 

This  reasoning  applies  word  for  word  to  the  develop- 
ment of  Bacteria  from  that  floating  matter  which  the 
electric  beam  reveals  in  the  air,  and  in  the  absence  of 
which  no  Bacterial  life  has  been  generated.  There  seems 
no  flaw  in  this  reasoning ;  and  it  is  so  simple  as  to  render 
it  unlikely  that  the  notion  of  Bacterial  life  developed 


PUTREFACTION   AND    INFECTION.  19 

from  dead  dust  can  ever  gain  currency  among  the  members 
of  a  great  scientific  profession. 

A  novel  mode  of  experiment  has  been  here  pursued, 
and  it  may  be  urged  that  the  conditions  laid  down  by 
other  investigators  in  this  field,  which  have  led  to  different 
results,  have  not  been  strictly  adhered  to.  To  secure 
accuracy  in  relation  to  this  point,  I  will  quote  the  latest 
words  of  a  writer  on  this  question,  who  has  materially 
influenced  medical  thought  both  in  this  country  and  in 
America.  '  We  know,'  he  says,  c  that  boiled  turnip-  or  hay- 
infusions  exposed  to  ordinary  air,  exposed  to  filtered  air, 
to  calcined  air,  or  shut  off  altogether  from  contact  with 
air,  are  more  or  less  prone  to  swarm  with  Bacteria  and 
vibriones  in  the  course  of  from  two  to  six  days.'  Who  the 
'  we '  are  who  possess  this  knowledge  is  not  stated.  I 
certainly  am  not  among  the  number,  though  I  have  sought 
anxiously  for  knowledge  of  the  kind.  The  statements 
were  thus  tested  in  succession. 

And  first,  with  regard  to  filtered  air.  A  group  of 
twelve  large  test-tubes  was  caused  to  pass  air-tight 
through  a  slab  of  wood.  The  wood  was  coated  with 
cement,  in  which,  while  hot,  a  heated  '  propagating  glass  " 
resembling  a  large  bell-jar  was  imbedded.  The  air 
within  the  jar  was  pumped  out  several  times,  air  filtered 
through  a  plug  of  cotton-wool  being  permitted  to  supply 
its  place.  The  test-tubes  contained  infusions  of  hay, 
turnip,  beef,  and  mutton — three  of  each — twelve  in  all. 
After  months  of  exposure  they  are  as  clear  and  cloudless 
to-day  as  they  were  upon  the  day  of  their  introduction ; 
while  twelve  similar  tubes,  prepared  at  the  same  time,  in 
precisely  the  same  way,  and  exposed  to  the  ordinary  air, 
are  clogged  with  mycelium,  mould,  and  Bacteria. 

With  regard  to  the  calcined  air,  a  similar  propagating 
glass  was  caused  to  cover  twelve  other  tubes  filled  with 
the  same  infusions.  The  4  glass '  was  exhausted  and  care- 


10]  FRAGMENTS   OF   SCIENCE. 

fully  filled  with  air,  which  had  been  slowly  passed  through 
a  red-hot  platinum  tube,  containing  a  roll  of  red-hot  plati- 
num gauze.  Tested  by  the  searching  beam,  the  calcined 
air  was  found  quite  free  from  floating  matter.  Not  a  speck 
has  invaded  the  limpidity  of  the  infusions  exposed  to  it, 
while  twelve  similar  tubes  placed  outside  have  fallen  into 
rottenness. 

The  experiments  with  calcined  air  took  another  form. 
Six  years  ago  I  found  that,  to  render  the  laboratory  air 
free  from  floating  matter,  it  was  only  necessary  to  permit 
a  platinum  wire  heated  to  whiteness  to  act  upon  it  for  a 
sufficient  time.  Shades,  containing  pear  juice,  damson 
juice,  infusions  of  hay  and  turnip,  and  water  of  yeast,  were 
freed  from  their  floating  matter  in  this  way.  The  infu- 
sions were  subsequently  boiled  and  permitted  to  remain 
in  contact  with  the  calcined  air.  They  are  quite  clear  to 
the  present  hour,  while  the  same  infusions  exposed  to 
common  air  became  mouldy  and  rotten  long  ago. 

It  has  been  affirmed  by  other  writers  on  this  question 
that  turnip-  and  hay-infusions  rendered  slightly  alkaline 
are  particularly  prone  to  exhibit  the  phenomena  of  spon- 
taneous generation.  This  was  not  found  to  be  the  case 
in  the  present  investigation.  Many  such  infusions  have 
been  prepared,  and  they  have  continued  for  months  with- 
out sensible  alteration. 

Finally,  with  regard  to  infusions  wholly  withdrawn 
from  air,  a  group  of  test-tubes,  containing  different  infu- 
sions, was  boiled  under  a  bell-jar  first  filled  with  filtered 
air,  and  from  which  the  air  was  subseqxiently  removed  as 
far  as  possible  by  a  good  air-pump.  They  are  now  as 
pellucid  as  they  were  at  the  time  of  their  preparation 
more  than  three  months  ago,  while  a  group  of  correspond- 
ing tubes  exposed  to  the  laboratory  air  have  all  fallen 
into  rottenness. 

There  is  still  another  form  of  experiment  on   which 


PUTREFACTION  AND    INFECTION.  [11 

great  weight  has  been  laid — that  of  hermetically  sealed 
tubes.  On  April  6  last,  a  discussion  on  the '  Germ  Theory 
of  Disease '  was  opened  before  the  Pathological  Society  of 
London.  The  meeting  was  attended  by  many  distin- 
guished medical  men,  some  of  whom  were  profoundly 
influenced  by  the  arguments,  and  none  of  whom  disputed 
the  facts  brought  forward  against  the  theory  on  that  occa- 
sion. The  following  important  summary  of  these  was 
then  given  by  Dr.  Bastian  :  c  ^^7ith  the  view  of  settling 
these  questions,  therefore,  we  may  carefully  prepare  an 
infusion  from  some  animal  tissue,  be  it  muscle,  kidney,  Or 
liver ;  we  may  place  it  in  a  flask  whose  neck  is  drawn  out 
and  narrowed  in  the  blowpipe-flame,  we  may  boil  the 
fluid,  seal  the  vessel  during  ebullition,  and,  keeping  it  in 
a  warm  place,  may  await  the  result,  as  I  have  often  done. 
After  a  variable  time,  the  previously  heated  fluid  within 
the  hermetically  sealed  flask  swarms  more  or  less  plenti- 
fully with  Bacteria  and  allied  organisms.' 

Previous  to  reading  this  statement,  I  had  operated 
upon  sixteen  tubes  of  hay-  and  turnip-infusions,  and  upon 
twenty-one  tubes  of  beef,  mackerel,  eel,  oyster,  oatmeal, 
malt,  and  potato,  hermetically  sealed  while  boiling,  not  by 
the  blowpipe,  but  by  the  far  more  handy  spirit-lamp  flame. 
In  no  case  was  any  appearance  whatever  of  Bacteria  or 
allied  organisms  observed.  The  perusal  of  the  discussion 
just  referred  to  caused  me  to  turn  again  to  muscle,  liver, 
and  kidney,  with  a  view  of  varying  and  multiplying  the 
evidence.  Fowl,  pheasant,  snipe,  partridge,  plover,  wild- 
duck,  beef,  mutton,  heart,  tongue,  lungs,  brains,  sweet- 
Iread,  tripe,  the  crystalline  lens,  vitreous  humour,  herring, 
haddock,  mullet,  codfish,  sole,  were  all  embraced  in  the 
experiments.  There  was  neither  mistake  nor  ambiguity 
about  the  result.  On  January  13  one  hundred  and  thirty- 
nine  of  the  flasks  operated  on  were  submitted  to  the  Fellows 
of  the  Royal  Society,  and  not  one  of  this  cloud  of  witnesses 


12]  FRAGMENTS   OF   SCIENCE. 

offered  the  least  countenance  to  the  assertion  that  liquids 
within  flasks,  boiled  and  hermetically  sealed,  swarm,  sub- 
sequently, more  or  less  plentifully  with  Bacteria  and 
allied  organisms. 

The  evidence  furnished  by  this  mass  of  experiments, 
that  Dr.  Bastian  must  have  permitted  errors  either  of 
preparation  or  observation  to  invade  his  work,  is,  I  sub- 
mit, very  strong.  But  to  err  is  human ;  and  in  an  en- 
quiry so  difficult  and  fraught  with  such  momentous  issues, 
it  is  not  error,  but  the  persistence  in  error  by  any  of  us 
for  dialectic  ends,  that  is  to  be  deprecated.  Let  me  here 
show  by  one  or  two  illustrations  the  risks  of  error  to 
which  I  have  been  exposed.  On  October  21  I  opened 
the  back-door  of  a  case  containing  six  test-tubes  filled 
with  an  infusion  of  turnip  which  had  remained  perfectly 
clear  for  three  weeks,  while  three  days  sufficed  to  crowd 
six  similar  tubes  exposed  to  mote-laden  air  with  Bacteria. 
With  a  small  pipette  I  took  specimens  from  the  pellucid 
tubes,  and  placed  them  under  the  microscope.  The  first 
tube  examined  showed  no  signs  of  life.  This  was  the  re- 
sult expected,  but  I  was  by  no  means  prepared  for  the  de- 
portment of  the  second  tube.  Here  the  exhibition  of  life 
was  monstrously  copious.  There  were  numerous  globular 
organisms,  which  revolved,  rotated,  and  quivered  in  the 
most  extraordinary  manner.  There  were  also  numbers  of 
lively  Bacteria  darting  to  and  fro.  An  experimenter  who 
ponders  his  work  and  reaches  his  conclusions  slowly,  can- 
not immediately  relinquish  them  ;  and  in  the  present  in- 
stance some  time  was  required  to  convince  me  that  I  had 
made  no  mistake.  I  could  find  none,  and  was  prepared  to 
accept  the  conclusion  that  in  the  boiled  infusion,  despite 
its  clearness,  life  had  appeared. 

But  in  a  protected  turnip-infusion,  which  had  been 
examined  on  October  13,  no  trace  of  life  cculd  be  found. 
In  this  case  perfect  transparency  was  accompanied  by  an 


PUTREFACTION  AND    INFECTION.  [13 

Titter  absence  of  life.  Indeed  the  selfsame  action  upon 
light  that  enabled  the  Bacteria  to  show  themselves  in 
the  microscope  must,  one  would  think,  infallibly  pro- 
duce turbidity.  Why,  moreover,  should  life  be  absent 
from  the  first  member  of  the  present  group  of  tubes  ?  I 
searched  this  again,  and  found  in  it  scanty  but  certain 
signs  of  life.  This  augmented  my  perplexity.  A  third 
tube  also  showed  scanty  traces  of  life.  Eeverting  to  the 
second  tube,  where  life  had  been  so  copious,  I  found 
that  in  it  the  organisms  had  become  as  scanty  as  in  the 
others.  I  confined  myself  for  a  time  to  the  three  tubes  of 
the  first  row  of  the  six,  going  over  them  again  and  again; 
sometimes  finding  an  organism  here  and  there,  but  some- 
times finding  nothing.  The  first  extraordinary  exhibition 
of  life  it  was  found  impossible  to  restore.  In  my  diffi- 
culty I  took  specimens  from  the  three  tubes  and  sent 
them  to  Professor  Huxley,  with  a  request  that  he  would 
be  good  enough  to  examine  them. 

On  the  22nd  my  search  was  extended  to  the  whole  of 
the  tubes.  Early  in  the  day  lively  Bacteria  were  found  in 
one  of  them  ;  later  on,  not  one  of  the  six  yielded  to  my 
closest  scrutiny  any  trace  of  life.  On  the  evening  of  the 
22nd  I  received  a  note  from  Mr.  Huxley  stating  that  a 
careful  examination  of  the  specimens  sent  to  him  revealed 
no  living  thing. 

Pipettes  had  been  employed  to  remove  the  solution 
from  the  test-tubes.  They  were  short  pieces  of  narrow 
glass  tubing,  drawn  out  to  a  point,  with  a  few  inches  of 
india-rubber  tubing  attached  to  them.  This  was  found 
convenient  for  bending  so  as  to  reach  the  bottom  of  the 
test-tubes.  Suspicion  fell  upon  this  india-rubber.  I 
washed  it,  and  examined  the  washing-water,  but  found  no 
life.  Distilled  water  had  been  used  to  cleanse  the 
pipettes,  and  on  the  morning  of  the  23rd  I  entered  the 
laboratory,  intending  to  examine  it.  Before  dipping  the 


14]  FRAGMENTS   OF   SCIENCE. 

pipette  into  the  water  I  looked  at  its  point.  The  tiniest 
drop  had  remained  in  it  by  capillary  attraction  from  the 
preceding  day.  This  I  blew  on  to  a  slide,  covered  it,  and 
placed  it  under  the  microscope.  An  astonishing  exhibi- 
tion of  life  was  my  reward.  Thus  on  the  scent,  I  looked 
through  my  pipettes,  and  found  two  more  with  the 
smallest  residual  drops  at  the  ends ;  both  of  them 
yielded  a  field  rampant  with  life.  The  Bacteria  darted 
in  straight  lines  to  and  fro,  bending  right  and  left  along 
the  line  of  motion,  wriggling,  rotating  longitudinally,  and 
spinning  round  a  vertical  transverse  axis.  Monads  also 
galloped  and  quivered  through  the  field.  From  one  of 
these  tiny  specks  of  liquid  I  obtained  an  exhibition  of  life 
not  to  be  distinguished  from  that  which  had  astonished 
me  on  the  21st. 

Obviously  the  phenomenon  then  observed  was  due  to 
the  employment  of  an  unclean  pipette.  Equally  obvious 
is  it  that  in  enquiries  of  this  nature  the  experimenter  is 
beset  with  danger,  the  grossest  errors  being  possible  when 
there  is  the  least  lack  of  care. 

Again,  three  tubes,  containing  infusions  of  turnip,  hay, 
and  mutton,  were  boiled  on  November  2,  under  a  bell-jar 
containing  air  so  carefully  filtered  that  the  most  searching 
examination  by  a  concentrated  beam  failed  to  reveal  a 
particle  of  floating  matter.  At  the  present  time  every 
one  of  the  tubes  is  thick  with  mycelium  and  covered  with 
mould.  Here  surely  we  have  a  case  of  spontaneous  gene- 
ration. Let  us  look  to  its  history. 

After  the  air  has  been  expelled  from  a  boiling  liquid 
it  is  difficult  to  continue  the  ebullition  without  '  bump- 
ing.' The  liquid  remains  still  for  intervals  and  then  rises 
with  sudden  energy.  It  did  so  in  the  case  now  under 
consideration,  and  one  of  the  tubes  boiled  over,  the  liquid 
overspreading  the  resinous  surface  in  which  the  bell-jar 
was  imbedded.  For  three  weeks  the  infusions  had  re- 


PUTREFACTION   AND    INFECTION.  \lb 

mained  perfectly  clear.     At  the  end  of  this  time,  with  a 
view  of  renewing  the  air  of  the  jar,  it  was  exhausted,  and 
refilled  by  fresh  air  which  had  passed  through  a  plug  of 
cotton-wool.     As  the  air  entered,  two  small  spots  of  peni- 
cillium,  resting  on  the  liquid  which  had  boiled  over,  at- 
tracted attention.    I  at  once  remarked  that  the  experiment 
was  a  dangerous  one,  as  the  entering  air  would  probably 
detach  some  of  the  spores  of  the  penicillium  and  diffuse 
them  in   the    bell-jar.     This  was,   therefore,  filled  very 
slowly,  so  as  to  render  the  disturbance  a  minimum.     Next 
day,  however,  a  tuft  of  mycelium  was  observed  at  the 
bottom  of  one  of  the  three  tubes,  namely  that  containing 
the  hay-infusion.     It  has  by  this  time  grown  so  as  to  fill 
a  large  portion  of  the  tube.     For  nearly  a  month  longer 
the  two  tubes  containing  the  turnip-  and  mutton-infusions 
maintained  their  transparency  unimpaired.     Late  in  De- 
cember  the    mutton-infusion,  which  was    in    dangerous 
proximity  to  the  outer  mould,  showed  a  tuft  upon  its 
surface.     The  turnip-infusion  continued  bright  and  clear 
for  nearly  a  fortnight  longer.     The  recent  cold  weather 
caused  me  to  add  a  third  gas-stove  to  the  two  which  had 
previously  warmed  the  room  in  which  the  experiments  are 
conducted.     The  warmth  played  upon  one  side  of  the 
bell-jar,  causing  currents  within  it;  and  the  day  after  the 
lighting  of  the  stove,  the  turnip-infusion  gave  birth  to  a 
tuft  of  mycelium.     In  this  case  the  small  spots  of  peni- 
cillium might  have  readily  escaped  attention ;  and  had 
they  done  so,  we  should  have  had  three  cases  of  '  spon- 
taneous generation '  far  more  striking  than   many  that 
have  been  adduced. 

In  further  illustration  of  the  danger  incurred  in  this 
field  of  enquiry,  I  may  refer  to  the  excellent  paper  of  Dr. 
Roberts  on  Biogenesis,  in  the  '  Philosophical  Transactions 
for  1874.'  Dr.  Roberts  fills  the  bulb  of  an  ordinary 
pipette  up  to  about  two-thirds  of  its  capacity  with  the 
2 


1C'  FRAGMENTS  OF  SCIENCE. 

infusion  to  be  examined.  In  the  neck  of  the  pipette  he 
places  a  plug  of  dry  cotton-wool.  He  then  hermetically 
seals  the  neck,  and  dips  the  bulb  into  boiling  water,  or 
hot  oil,  where  he  permits  it  to  remain  for  the  requisite 
time.  Here  we  have  no  disturbance  from  ebullition,  and 
no  loss  by  evaporation.  The  bulb  is  removed  from  the 
hot  water  and  permitted  to  cool.  The  sealed  end  of  the 
neck  is  then  filed  off,  the  cotton-wool  alone  interposing 
between  the  infusion  and  the  atmosphere. 

The  arrangement  is  beautiful,  but  it  has  one  weak 
point.  Cotton-wool  free  from  germs  is  not  to  be  found, 
and  the  plug  employed  by  Dr.  Eoberts  infallibly  contained 
them.  In  the  gentle  movement  of  the  air  to  and  fro,  as 
the  temperature  changed,  or  by  any  shock,  jar,  or  motion 
to  which  the  pipette  might  be  subjected,  we  have  cer- 
tainly a  cause  sufficient  to  detach  a  germ  now  and  then 
from  the  cotton-wool  which,  falling  into  the  infusion, 
would  produce  its  effect.  Probably  also  condensation  oc- 
curred at  times  in  the  neck  of  the  pipette,  the  water  of 
condensation  carrying  back  from  the  cotton-wool  the  seeds 
of  life.  The  fact  of  fertilisation  being  so  rare,  as  Dr. 
Roberts  found  it  to  be,  is  a  proof  of  the  care  with  which 
his  experiments  were  conducted.  But  he  did  find  cases  of 
fertilisation  after  prolonged  exposure  to  the  boiling  tem- 
perature ;  and  this  caused  him  to  come  to  the  conclusion 
that  under  certain  rare  conditions  spontaneous  generation 
may  occur.  He  also  found  that  an  alkalised  hay-infusion 
was  so  difficult  to  sterilise  that  it  was  capable  of  with- 
standing the  boiling  temperature  for  hours  without  losing 
its  power  of  generating  life.  Careful  experiments  have 
been  made  with  this  infusion.  Dr.  Roberts  is  certainly 
correct  in  assigning  to  it  superior  nutritive  power.  But 
in  the  present  enquiry  five  minutes'  boiling  sufficed  to 
completely  sterilise  the  liquid. 

I  shall  hardly  be  charged  with  any  desire  to  limit  the 


PUTREFACTION  AND   INFECTION.  [17 

power  and  potency  of  matter  in  regard  to  life.  On  this 
point  I  have  already  expressed  myself  in  a  manner  not  to 
be  mistaken.  But,  holding  the  notions  I  do,  it  is  all 
the  more  incumbent  on  me  to  affirm  that,  as  far  as  en- 
quiry has  hitherto  penetrated,  life  has  never  been  proved 
to  appear  independently  of  antecedent  life. 

With  regard  to  the  general  diffusion  of  germs  in  the 
atmosphere,  the  notions  entertained  by  distinguished 
writers  rendered  it  desirable  to  place  the  point  beyond 
question.  At  Down,  Mr.  Darwin  and  Mr.  Francis  Darwin ; 
at  High  Elms,  Sir  John  Lubbock  ;  at  Sherwood,  near  Tun- 
bridge  Wells,  Mr.  Siemens  ;  at  Pembroke  Lodge,  Eich- 
mond  Park,  Mr.  Rollo  Eussell ;  at  Heathfield  Park,  Miss 
Hamilton  ;  at  Greenwich  Hospital,  Mr.  Hirst ;  at  Kew,  Dr. 
Hooker  ;  and  at  the  Crystal  Palace,  Mr.  Price  kindly  took 
charge  of  infusions,  every  one  of  which  was  invaded,  many 
by  astounding  swarms  of  organisms. 

To  obtain  more  definite  insight  regarding  the  diffusion 
of  atmospheric  germs  a  square  wooden  tray  was  pierced  with 
100  holes,  into  each  of  which  was  dropped  a  short  test-tube. 
On  October  23  thirty  of  these  tubes  were  filled  with  an 
infusion  of  hay,  thirty-five  with  an  infusion  of  turnip,  and 
thirty-five  with  an  infusion  of  beef.  The  tubes,  with  their 
infusions,  had  been  previously  boiled,  ten  at  a  time,  in  an 
oil-bath.  One  hundred  circles  were  marked  on  paper,  so  as 
to  form  a  map  of  the  tray,  and  every  day  the  state  of  each 
tube  was  registered  upon  the  corresponding  circle.  In  the 
following  description  the  term  '  cloudy  '  is  used  to  denote 
the  first  stage  of  turbidity,  distinct  but  not  strong ;  the 
term  '  muddy '  is  used  to  denote  thick  turbidity. 

One  tube  of  the  hundred  was  first  singled  out  and  ren- 
dered muddy.  It  belonged  to  the  beef-group,  and  it  was  a 
whole  day  in  advance  of  all  the  other  tubes.  The  progress 
of  putrefaction  was  first  registered  on  October  26.  The 
*  map  '  then  taken  may  be  thus  described  : 


18]  FRAGMENTS  OF   SCIENCE. 

Hay. — Of  the  thirty  specimens  exposed  one  had 
become  *  muddy  ' — the  seventh  in  the  middle  row  reckon- 
ing from  the  side  of  the  tray  nearest  a  stove.  Six  tubea 
remained  perfectly  clear  between  this  muddy  one  and  the 
stove,  proving  that  differences  of  warmth  may  be  over- 
ridden by  other  causes.  Every  one  of  the  other  tubes 
containing  the  hay-infusion  showed  spots  of  mould  upon 
the  clear  liquid. 

Turnip. — Four  of  the  thirty-five  tubes  were  very 
muddy,  two  of  them  being  in  the  row  next  the  stove,  one 
four  rows  distant,  and  the  remaining  one  seven  rows 
away.  Besides  these,  six  tubes  had  become  clouded 
There  was  no  mould  on  any  of  the  tubes. 

Beef. — One  tube  of  the  thirty-five  was  quite  muddy, 
iii  the  seventh  row  from  the  stove.  There  were  three 
cloudy  tubes,  while  seven  of  them  bore  spots  of  mould. 

As  a  general  rule,  organic  infusions  exposed  to  the  air 
during  the  autumn  remained,  for  two  days  or  more 
perfectly  clear.  Doubtless  from  the  first  germs  fell  into 
them,  but  they  required  time  to  be  hatched.  This  period 
of  clearness  may  be  called  the  *  period  of  latency,'  and 
indeed  it  exactly  corresponds  with  what  is  understood  by 
this  term  in  medicine.  Towards  the  end  of  the  period  of 
latency  the  fall  into  a  state  of  disease  is  comparatively 
sudden ;  the  infusion  passing  from  perfect  clearness  to 
cloudiness  more  or  less  dense  in  a  few  hours. 

Thus  the  tube  placed  in  Mr.  Darwin's  possession  was 
clear  at  8.30  A.M.  on  October  19,  and  cloudy  at  4.30  P.M. 
Seven  hours,  moreover,  after  the  first  record  of  our  tray 
of  tubes,  a  marked  change  had  occurred.  Instead  of  one, 
eight  of  the  tubes  containing  hay-infusion  had  fallen  into 
uniform  muddiness.  Twenty  others  had  produced  Bac- 
terial slime,  which  had  sunk  to  the  bottom,  every  tube 
containing  the  slime  being  covered  by  mould.  Three 
tubes  only  remained  clear,  but  with  mould  upon  their 


PUTREFACTION-  AND    INFECTION.  [19 

surfaces.  The  muddy  turnip-tubes  had  increased  from 
four  to  ten ;  seven  tubes  were  clouded,  while  eighteen  of 
them  remained  clear,  with  here  and  there  a  speck  of 
mould  on  the  surface.  Of  the  beef,  six  were  cloudy  and 
one  thickly  muddy,  while  spots  of  mould  had  formed  in 
the  majority  of  the  remaining  tubes.  Fifteen  hours  sub- 
sequent to  this  observation,  viz.  on  the  morning  of 
October  27,  all  the  tubes  containing  hay-infusion  were 
smitten,  though  in  different  degrees,  some  of  them  being 
much  more  turbid  than  others.  Of  the  turnip-tubes, 
three  only  remained  unsmitten,  and  two  of  these  had 
mould  upon  their  surfaces.  Only  one  of  the  thirty-five 
beef-infusion  remained  intact.  A  change  of  occupancy, 
moreover,  had  occurred  in  the  tube  which  first  gave  way. 
Its  muddiness  remained  grey  for  a  day  and  a  half,  then  it 
changed  to  bright  yellow  green,  and  it  maintained  this 
colour  to  the  end.  On  the  27th  every  tube  of  the  hun- 
dred was  smitten,  the  majority  with  uniform  turbidity ; 
some,  however,  with  mould  above  and  slime  below,  the 
intermediate  liquid  being  tolerably  clear.  The  whole 
process  bore  a  striking  resemblance  to  the  propagation  of 
a  plague  among  a  population,  the  attacks  being  successive, 
and  of  different  degrees  of  virulence. 

From  the  irregular  manner  in  which  the  tubes  are 
infected  we  may  infer  that,  as  regards  quantity,  the 
distribution  of  the  germs  in  the  air  is  net  uniform.  The 
singling  out,  moreover,  of  one  tube  of  the  hundred  by 
the  particular  Bacteria,  that  develop  a  green  pigment, 
shows  that,  as  regards  quality,  the  distribution  is  not 
uniform.  The  same  absence  of  uniformity  was  manifested 
in  the  struggle  for  existence  between  the  Bacteria  and 
the  penicillium.  In  some  tubes  the  former  were  tri- 
umphant; in  other  tubes,  of  the  same  infusion,  the  latter 
was  triumphant.  It  would  seem  also  as  if  a  want  of 
uniformity  as  regards  vital  vigour  prevailed.  With  the 


20]  FRAGMENTS   OF   SCIENCE. 

selfsame  infusion  the  motions  of  the  Bacteria  in  some 
tubes  were  exceedingly  languid,  while  in  other  tubes  they 
resembled  a  rain  of  projectiles,  being  so  rapid  and  violent 
as  to  be  followed  with  difficulty  by  the  eye.  Reflecting 
on  the  whole  of  this,  I  conclude  that  the  germs  float 
through  the  atmosphere  in  groups  or  clouds,  with  spaces 
more  sparsely  filled  between  them.  The  touching  of  a 
nutritive  fluid  by  a  Bacterial  cloud  would  naturally 
have  a  different  effect  from  the  touching  of  it  by  the 
interspace  between  two  clouds.  But  as,  in  the  case  of  a 
mottled  sky,  the  various  portions  of  the  landscape  are 
successively  visited  by  shade,  so,  in  the  long  run,  were 
the  various  tubes  of  the  tray  touched  by  the  Bacterial 
clouds,  the  final  fertilisation  or  infection  of  them  all 
being  the  consequence.  These  results  connect  themselves 
with  tbe  experiments  of  Pasteur  on  the  non-continuity  of 
the  cause  of  so-called  spontaneous  generation,  and  with 
other  experiments  of  my  own.1 

On  November  9  a  second  tray,  containing  100  tubes 
filled  with  an  infusion  of  mutton,  was  exposed  to 
the  air.  On  the  morning  of  the  llth  six  of  the  ten 
nearest  the  stove  had  given  way  to  putrefaction,  Three 
of  the  row  most  distant  from  the  stove  had  yielded, 
while  here  and  there  over  the  tray  particular  tubes 
were  singled  out  and  smitten  by  the  infection.  Of  the 
whole  tray  of  100  tubes,  twenty-seven  were  either 

1  In  hospital  practice  the  opening  of  a  wound  during  the  passage  of  a 
Bacterial  cloud  would  have  an  effect  very  different  from  the  opening  of  it 
in  the  interspace  between  two  clouds.  Certain  caprices  in  the  behaviour 
of  dressed  wounds  may  possibly  be  accounted  for  in  this  way. 

Under  the  heading  •  Nothing  New  under  the  Sun,'  Professor  Huxley  has 
just  sent  me  the  following  remarkable  extract: — '  Uebrigens  kann  man  sich 
die  in  der  Atmosphare  sehwimmenden  Thierchen  wie  Wolken  denken,  mit 
denen  ganz  leere  Luftmassen,  ja  gauze  Tage  vollig  ioinen  Luftverhaltnis^e 
wechseln.'  (Ehrenberg,  'Infusions  Thierehen,'  1838,  p.  525.)  The  coinci- 
dence of  phraseology  is  surprising,  for  I  knew  nothing  of  Ehrenberg's  con- 
ception. My  '  clouds,'  however,  are  but  small  miniatures  of  his. 


PUTKEFACTION   AND    INFECTION.  [21 

muddy  or  cloudy  on  the  llth.  Thus,  doubtless,  in  a  con- 
tagious atmosphere,  are  individuals  successively  struck 
down.  On  the  12th  all  the  tubes  had  given  way,  but  the 
differences  in  their  contents  were  extraordinary.  All  of 
them  contained  Bacteria,  some  few,  others  in  swarms. 
In  some  tubes  they  were  slow  and  sickly  in  their  motions, 
in  some  apparently  dead,  while  in  others  they  darted 
about  with  rampant  vigour.  These  differences  are  to  be 
referred  to  differences  in  the  germinal  matter,  for  the 
same  infusion  was  presented  everywhere  to  the  air.  Here 
also  we  have  a  picture  of  what  occurs  during  an  epidemic, 
the  difference  in  number  and  energy  of  the  Bacterial 
swarms  resembling  the  varying  intensity  of  the  disease. 
It  becomes  obvious  from  these  experiments  that  of  two 
individuals  of  the  same  population,  exposed  to  a  conta- 
gious atmosphere,  the  one  may  be  severely,  the  other 
lightly  attacked,  though  the  two  individuals  may  be  as 
identical  as  regards  susceptibility  as  two  samples  of  one 
and  the  same  mutton- infusion.  Experiments  with  other 
trays  are  described  in  the  full  account  of  this  investigation, 
and  calculations  are  made  which  prove  the  error  of  the 
assertion  that  the  germs  are  but  scantily  distributed 
through  the  air.  There  are  billions  of  them  in  every 
ordinary  London  room. 

The  parallelism  of  these  actions  with  the  progress  of 
infectious  disease  may  be  traced  still  further.  The 
'  Times '  of  January  1 7  contained  a  letter  on  typhoid 
fever,  signed  '  M.D.,'  in  which  occurred  the  following 
remarkable  statement :  '  In  one  part  of  it  [Edinburgh], 
congregated  together  and  inhabited  by  the  lowest  of  the 
population,  there  are,  according  to  the  Corporation  return 
for  1874,  no  less  than  14,319  houses  or  dwellings — many 
under  one  roof,  on  the  '  flat '  system — in  which  there 
are  no  house  connections  whatever  with  the  street  sewers, 
and,  consequently,  no  water-closets.  To  this  day.,  there- 


22]  FRAGMENTS   OF   SCIENCE. 

fore,  all  the  excrementitious  and  other  refuse  of  the  in- 
habitants is  collected  in  pails  or  pans,  and  remains  in  their 
midst,  generally  in  a  partitioned-off  corner  of  the  living- 
room,  until  the  next  day,  when  it  is  taken  down  to  the 
streets  and  emptied  into  the  Corporation  carts.  Drunken 
and  vicious  though  the  population  be,  herded  together 
like  sheep,  and  with  the  filth  collected  and  kept  for  twenty- 
four  hours  in  their  very  midst,  it  is  a  remarkable  fact  that 
typhoid  fever  and  diphtheria  are  simply  unknown  in 
these  wretched  hovels.' 

This  case  has  its  analogue  in  the  following  experi- 
ment, which  is  representative  of  a  class :  On  November 
30  a  quantity  of  animal  refuse,  embracing  beef, 
fish,  rabbit,  hare,  was  placed  in  two  large  test-tubes 
opening  into  a  protecting-chamber  containing  six  tubes. 
On  December  13,  when  the  refuse  was  in  a  state  of 
noisome  putrefaction,  infusions  of  -whiting,  turnip,  beef, 
and  mutton  were  placed  in  the  other  four  tubes.  They 
were  boiled  and  abandoned  to  the  action  of  the  foul '  sewer- 
gas  '  emitted  by  their  two  putrid  companions.  On 
Christmas-day  these  four  infusions  were  limpid.  The 
end  of  the  pipette  was  then  dipped  into  one  of  the  putrid 
tubes,  and  a  quantity  of  matter,  comparable  in  smallness 
to  the  pock-lymph,  held  on  the  point  of  a  lancet,  was 
transferred  to  the  turnip.  Its  clearness  was  not  sensibly 
affected  at  the  time ;  but  on  the  following  day  it  was 
turbid  throughout.  On  the  27th  a  speck  from  the  in- 
fected turnip  was  transferred  to  the  whiting;  on  the 
2Hth  disease  had  taken  entire  possession  of  the  whiting. 
To  the  present  hour  the  beef-  and  mutton-tubes  remain  as 
limpid  as  distilled  water.  Just  as  in  the  case  of  the 
living  men  and  women  in  Edinburgh,  no  amount  of 
fetid  gas  had  the  power  of  propagating  the  plague  as  long 
as  the  organisms  which  constitute  the  true  contagium  did 
not  gain  access  to  the  infusions. 


PUTREFACTION   AND    INFECTION.  [23 

The  universal  prevalence  of  the  germinal  matter  of 
Bacteria  in  water  has  been  demonstrated  with  the  utmost 
evidence  by  the  experiments  of  Dr.  Eurdon  Sanderson. 
But  the  germs  in  water  are  in  a  very  different  condition, 
as  regards  readiness  for  development,  from  those  in  air. 
In  water  they  are  thoroughly  wetted,  and  ready,  under 
the  proper  conditions,  to  pass  rapidly  into  the  finished 
organism.  In  air  they  are  more  or  less  desiccated,  and 
require  a  period  of  preparation  more  or  less  long  to  bring 
them  up  to  the  starting-point  of  the  water-germs.  The 
rapidity  of  development  in  an  infusion  infected  by  either 
a  speck  of  liquid  containing  Bacteria  or  a  drop  of  water 
is  extraordinary.  On  January  4  a  thread  of  glass 
almost  as  fine  as  a  hair  was  dipped  into  a  cloudy  turnip- 
infusion,  and  the  tip  only  of  the  glass  fibre  was  introduced 
into  a  large  test-tube  containing  an  infusion  of  red  mullet. 
Twelve  hours  subsequently  the  perfectly  pellucid  liquid 
was  cloudy  throughout.  A  second  test-tube  containing 
the  same  infusion  was  infected  with  a  single  drop  of  the 
distilled  water  furnished  by  Messrs.  Hopkin  and  Williams ; 
twelve  hours  also  sufficed  to  cloud  the  infusion  thus 
treated.  Precisely  the  same  experiments  were  made  with 
herring  with  the  same  result.  At  this  season  of  the  year 
several  days'  exposure  to  the  air  is  needed  to  produce 
the  same  effect.  On  December  31  a  strong  turnip- 
infusion  was  prepared  by  digesting  in  distilled  water 
at  a  temperature  of  120°  Fahr.  The  infusion  was 
divided  between  four  large  test-tubes,  in  one  of  which  it 
was  left  unboiled,  in  another  boiled  for  five  minutes,  and 
in  the  two  remaining  ones  boiled,  and,  after  cooling,  in- 
fected with  one  drop  of  beef-infusion  containing  Bacteria. 
In  twenty-four  hours  the  unboiled  tube  and  the  two  in- 
fected ones  were  cloudy,  the  unboiled  tube  being  the 
most  turbid  of  the  three.  The  infusion  here  was  pecu- 
liarly limpid  after  digestion ;  for  turnip  it  was  quite 


24]  FRAGMENTS   OF   SCIENCE. 

exceptional,  and  no  amount  of  searching  with  the  micro- 
scope sufficed  to  reveal  in  it,  at  first,  the  trace  of  a  living 
Bacterium ;  still  germs  were  t'uere  which,  suitably 
nourished,  passed  in  a  single  day  into  Bacterial  swarms 
without  number.1  Five  days  did  not  suffice  to  produce 
an  effect  approximately  equal  to  this  in  the  boiled  tube, 
which  was  uninfected  but  exposed  to  the  common  labora- 
tory air. 

There  cannot,  moreover,  be  a  doubt  that  the  germs  in 
the  air  differ  widely  among  themselves  as  regards  pre- 
paredness for  development.  Some  are  fresh,  others  old  ; 
some  are  dry,  others  moist.  Infected  by  such  germs,  the 
same  infusion  would  require  different  lengths  of  time 
to  develop  Bacterial  life.  This  remark  applies  to  and 
probably  explains  the  different  degrees  of  rapidity  with 
which  epidemic  disease  acts  upon  different  people.  In 
some  the  hatching-period,  if  it  maybe  called  such,  is  long, 
in  some  short,  the  differences  depending  upon  the  different 
degrees  of  preparedness  of  the  contagium. 

Such  is  an  outline  of  the  present  enquiry  as  far  as  it 
is  now  complete.  It  gives  me  pleasure  to  refer  to  the 
untiring  patience,  the  admirable  mechanical  skill,  the 
veracity  in  thought,  word,  and  deed  displayed  throughout 
by  my  assistant,  Mr.  John  Cottrell,  who  was  zealously 
aided  by  his  junior  colleague,  Mr.  Frank  Valter. 


MY  interest  in  the  question  of  spontaneous  generation 
was  first  excited  by  the  imperishable  investigations  of 
Pasteur,  while  the  medical  bearings  of  the  question  were 
subsequently  made  more  and  more  clear  to  me,  mainly,  I 

1  The  gprms  are  to  be  found  in  the  heart  of  the  clearest  blocks  of 
Norway  ice.  Such  -water  prepared  by  myself  has  been  examined  by  Dr, 
Sanderson,  and  found  to  bo  quite  as  infectious  as  ordinary  -water. 


PUTREFACTION  AND    INFECTION.  [25 

ought  to  say,  by  the  writings  and  conversation  of  Dr. 
William  Budd.  For  more  than  fifteen  years  this  strong 
and  original  thinker  fought  in  England  an  up-hill  fight 
in  favour  of  the  germ  theory  of  epidemic  disease,1  and  his 
last  intellectual  effort,  the  production  of  his  great  work 
on  Typhoid  Fever,  under  which,  unhappily,  his  over-active 
mind  gave  way,  consisted  in  conclusively  demonstrating 
both  the  contagious  character  and  the  seat  of  the  con- 
tagium  of  that  disease.  The  quotation  from  a  letter  given 
at  page  172  of  this  volume  will  show  the  clearness  and 
definiteness  with  which  Dr.  Budd  from  the  first  grasped 
the  doctrine  of  'the  vitality  of  contagia'  which  is  now 
everywhere  gaming  ground. 

Since  the  time  here  referred  to,  able  investigators  in 
various  European  countries  have  taken  up  the  question  of 
contagium,  until  at  the  present  moment  no  other  medical 
principle  occupies  so  much  thought,  or  is  the  subject  of  so 
much  discussion.  '  How  does  it  happen,'  says  Dr.  Burdon 
Sanderson,2  '  that  these  Bacteria,  which  we  suppose  must 
have  existed  half-a-dozen  years  ago  in  as  great  numbers 
as  at  present,  were  then  scarcely  heard  of,  and  that  they 
now  occupy  so  large  a  place  in  the  medical  literature  of 
this  country  and  of  Germany,  and  have  lately  afforded 
material  for  lively  discussion  in  the  French  Academy  ? ' 
Dr.  Sanderson  points  out  the  relation  of  Lister  in  England 
and  of  Hallier  in  Germany  to  the  movement  regarding 
Bacteria  which  is  now  working  like  a  ferment  through 
the  medical  world.  But  to  scarcely  any  other  workers  are 
we  more  indebted  than  to  Dr.  Sanderson  and  his  colleagues, 
for  the  continued  and  successful  prosecution  of  researches 
bearing  upon  the  pathology  of  contagion. 

I,  this  year,  took  with  me  to  the  Alps  the  excellent 

1  Supported,  I  am  happy  to  say,  by  one  eminent  authority,  Sir  Thomas 
Watson. 

*  'British  Medical  Journal.'  January  16,  1875. 


26J  FRAGMENTS   OP   SCIENCE. 

reports  of  the  medical  officer  of  the  Privy  Council,  toge- 
ther with  the  associated  memoirs  of  Dr.  Sanderson  and 
Dr.  Klein.  On  the  healthy  mountain  sides,  in  the 
intervals  of  other  work,  I  read  these  papers,  with  the 
interest  of  one  who  saw  in  them  the  steady  growth  and 
consolidation  of  a  principle  which  promises  to  rescue 
medicine  from  the  reproach  of  empiricism,  to  raise  it  to 
the  rank  of  a  true  science,  and  to  place  those  '  invisible 
foes,'  as  they  have  been  called  by  the  celebrated  Cohn, 
which  lurk  in  the  air  we  breathe  and  in  the  water  we 
drink,  within  the  grasp  of  the  physician. 

A  few  extracts  from  the  reports  with  which  Mr.  John 
Simon  prefaces  the  memoirs  of  the  gentlemen  who  work 
in  his  department,  will  show  what  important  advances 
have  been  made  of  late  years  in  our  knowledge  of  the 
contagia  of  infective  disease.  *  Ten  years  ago,'  says  Mr. 
Simon,  in  his  report  to  the  Privy  Council  for  1874,  'we 
had  not  even  a  beginning  of  any  true  insight  into  the 
respective  contagia  which  excite  acute  infective  diseases  ; 
and,  considering  the  large  and  lasting  interest  which 
exact  studies  in  this  field  of  scientific  research  must  have 
for  the  human  race,  I  think  the  fact  noteworthy  that  the 
first  of  such  studies  were  instituted  and  the  first  steps  of 
discovery  made  with  reference  to  a  contagious  fever  of 
horned  cattle.  I  refer,  namely,  to  the  researches  which 
were  made  under  Her  Majesty's  Government  in  1865,  in 
aid  of  the  then  Cattle-plague  Commission;  when  Dr.  Beale, 
working  at  the  microscopy  of  the  disease,  drew  attention 
to  the  swarms  of  extremely  minute  particles  which  he 
found  universally  present  in  the  textures  and  juices  .of  the 
animals,  and  which  he  believed  to  be  the  contagium  of 
the  disease;  and  when  Dr.  Sanderson,  working  r.t  the 
matter  from  a  different  point  of  view,  succeeded  in  show- 
ing experimentally  that  the  true  contagium  admits  of 
being  physically  distinguished  in  the  animal  juices  which 


PUTREFACTION   AND    INFECTION.  [27 

contain  it,  and  of  being  so  separated  from  them  as  to 
leave  them  without  infective  power.  In  the  next  suc- 
ceeding years  the  writings  of  Dr.  Hallier,  Professor  of 
Botany  in  Jena,  brought  under  animated  discussion,  as  a 
branch  of  microphytology,  the  nature  and  origin  of  conta- 
gium  particles  in  a  great  variety  of  diseases,  human  and 
brute.  New  experimental  knowledge  of  several  contagia 
was  set  forth  in  the  writings  of  Professor  Chauveau,  of 
the  Veterinary  School  of  Lyons,  and  in  1870  I  had  the 
honour  of  presenting  Dr.  Sanderson's  first  report  of  re- 
searches made  in  the  matter.  At  that  time  general  con- 
clusions seemed  justified,  first,  that  the  characteristic- 
shaped  elements  which  the  microscope  had  shown  abound- 
ing in  various  infective  products  are  self-multiplying 
organic  /orras,  not  congeneric  with  the  animal  body  in 
which  they  are  found,  but  apparently  of  the  lowest  vege- 
table kind ;  and  secondly,  that  such  living  organisms  are 
probably  the  essence,  or  an  inseparable  part  of  the  essence, 
of  all  contagia  of  disease.  The  study  of  morbid  contagion 
was  thus  brought  into  seeming  affinity  with  that  which 
had  for  some  years  before  been  made  by  Professor 
Schroeder  and  M.  Pasteur  in  the  ordinary  processes  of 
fermentation  and  putrefaction  ;  and  there  began  to  be 
faintly  visible  to  us  a  vast  destructive  laboratory  of  Nature, 
wherein  the  diseases  which  are  most  fatal  to  animal  life, 
and  the  changes  to  which  dead  organic  matter  is  pas- 
sively liable,  appear  bound  together  by  what  must  at 
least  be  called  a  very  close  analogy  of  causation.  This 
view  of  the  matter  has  since  then  become  greatly  more 
distinct,  in  consequence  of  the  investigations  made  by 
Dr.  Sanderson,  particularly  in  1871  and  1872,  with  refer- 
ence to  the  common  septic  contagium  or  ferment.  For 
in  that  ferment  there  seems  now  to  be  identified  a 
force  which,  acting  disintegratively  upon  organic  matter, 
whether  dead  or  living,  can  on  the  one  hand  initiate  putre- 


38]  FRAGMENTS   OF   SCIENCE. 

faction  of  what  is  dead,  and  on  the  other  hand  initiate 
febrile  and  inflammatory  processes  in  what  is  living. 

4  Continuation  of  this  line  of  study  in  regard  of  acute 
infections  of  the  living  body,  is  represented  in  the  first 
two  of  the  appended  papers. 

'  In  the  first  paper  Dr.  Sanderson  brings  down  to  the 
present  time  an  account  of  the  microphytes  of  contagion, 
setting  forth  more  particularly  such  positive  knowledge 
as  had  yet  been  obtained  with  regard  to  the  respective 
contagia  and  respective  morbid  processes  of  diphtheria, 
erysipelas,  relapsing  fever,  and  splenic  fever,  or  the  "milz- 
brand  "  of  veterinary  practice. 

*  The  second  paper  represents  a  contribution  to  the 
growing  modern  doctrine  of  contagion  in  an  exposition  by 
Dr.  Klein  of  the  intimate  nature  of  the  local  changes 
which  characterise  the  acute  zymotic  disease  known  as 
Variola  Ovina  or  Sheep-pox.  Dr.  Klein  has  been  able 
to  identify  the  contagium  particles  of  that  infectious  fever 
as  definite  microphytes  growing  and  fructifying  with  vast 
rapidity  in  the  canals  and  tissues  of  the  infected  skin. 
The  woodcuts  of  his  annexed  paper  show  the  process  to 
have  been  observed  by  him  with  a  completeness  not  yet,  I 
believe,  attained  in  regard  of  any  other  such  case.  And 
these  results  of  his,  while  they  complete,  as  regards  the 
special  disease  in  question,  the  broad  pathological  outline 
which  previous  inductions  had  rendered  probable,  must 
also,  I  think,  be  regarded  as  tending  very  importantly  to 
confirm,  while  they  illustrate,  the  general  doctrine  of  the 
vitality  of  contagia? 

It  was  with  no  levity  of  mind  that  I,  an  outsider,  who 
had  been  drawn  by  my  own  experiments  in  1868-69  to 
the  contemplation  of  the  subject,  ventured  to  range  my- 
self on  the  side  of  those  who  then  advocated  the  doctrine 
so  clearly  enunciated  by  Mr.  Simon,  and  so  vastly 
strengthened  by  the  researches  conducted  under  his 


PUTREFACTION  AND    INFECTION.  [29 

direction.  What  was  then  more  or  less  the  surmise  of 
men  of  genius  like  William  Budd,  is  now  being  raised 
to  the  level  of  demonstration.  With  increased  discipline 
investigation  naturally  tends  to  become  more  detailed 
and  specific,  the  forecasts  of  the  scientific  imagination 
becoming  gradually  displaced  by  the  solid  matter  of  fact. 
Speaking  of  the  havoc  produced  by  typhoid  fever  and  of 
the  contagion  to  which  that  fever  is  due,  Dr.  Budd,  in  his 
celebrated  work,1  observes :  *  It  is  humiliating  to  think 
that  issues  such  as  these  should  be  contingent  on  the 
powers  of  an  agent  so  low  in  the  scale  of  being  that  the 
mildew  which  springs  up  on  decaying  wood  must  be  con- 
sidered high  in  comparison.' 

In  his  last  report  to  the  Privy  Council  Mr.  Simon  was 
able  to  announce  the  probable  discovery  by  Dr.  Klein  of 
the  agent  here  referred  to.  After  passing  in  review  two 
important  papers  by  Professor  Burdon  Sanderson  on  the 
'  Process  of  Fever,'  and  on  the  c  Experimental  Study  of 
Infective  Inflammations,'  Mr.  Simon  thus  refers  to  Dr. 
Klein's  paper :  '  The  third  paper,  which  is  by  Dr.  Klein, 
gives  (as  foreshadowed  in  my  last  report)  the  extremely 
interesting  results  of  his  investigation  of  the  intimate 
anatomy  of  Enteric  Fever ;  and  Dr.  Klein,  who  fortunately 
is  artist  enough  to  reproduce  admirably  with  his  pencil 
the  anatomical  appearances  which  he  displays  under  the 
microscope,  has  here,  as  on  former  occasions,  illustrated 
his  written  report  with  drawings  'which  make  the  results 
peculiarly  clear. 

'  The  paper  has  its  distinctive  and  very  great  interest 
in  the  fact  that  it  purports  to  describe  for  the  first  time 
the  contagium  of  enteric  fever  as  something  cognisable  to 
the  eye :  in  respect  of  certain  multiplying  microscopical 
forms,  apparently  of  the  lowest  vegetable  life,  which  are 

1  '  Typhoid  Fever ;  its  Nature,  Mode  of  Spreading  and  Prevention. 
Longmans,  1873,  p.  4. 


50]  FRAGMENTS   OF   SCIENCE. 

found  in  innumerable  swarms  in  the  bowel-textures  and 
bowel  discharges  of  the  sick  ;  penetrating  from  the  former 
to  diffuse  throughout  the  patient's  general  system,1  and 
teeming  in  the  latter  to  represent,  as  this  view  supposes, 
the  possible  germs  of  epidemic  infection. 

'  The  most  cursory  glance  cast  by  the  anatomist  at  the 
illustrations  of  Dr.  Klein's  paper  will  convince  him  of  the 
reality  of  the  facts  which  Dr.  Klein  interprets  to  the 
above  effect:  and  that  the  interpretation  thus  assigned 
to  the  facts  is  the  one  which  they  must  generally  receive 
is,  I  think,  an  inevitable  consequence  of  the  considerations 
which  were  stated  in  my  last  report  with  general  regard 
to  agencies  of  contagion.  The  enteric  fever  of  man  is  not 
yet  known  to  be  communicable  to  any  other  animal ;  and 
it  has  therefore  not  been  possible  to  perform  in  relation 
to  its  supposed  contagium  such  experiments  as  have  been 
made  on  the  lower  animals  with  respect  to  the  contagia 
of  some  other  diseases.  In  absence  of  such  experiments, 
the  same  degree  of  certainty  cannot  at  present  be  ex- 
pressed with  regard  to  the  contagium  of  enteric  fever  as 
with  regard  to  that  (for  instance)  of  sheep-pox:  but, 
subject  to  any  correction  which  experiment  may  hereafter 
supply,  we  may  at  least  accept  as  approximately  proven, 
that  the  contagium  of  enteric  fever  has  its  essence,  or  part 
of  its  essence,  in  the  microphyte  which  Dr.  Klein  has 
discovered ;  and  that  here  accordingly  is  a  further  illus- 
tration of  the  general  doctrine  which  I  have  noticed  on 
many  previous  occasions,  with  regard  to  the  significance 
of  specific  organic  forms  in  the  constitution  of  specific 
contagia. 

In  an  immediately  practical  point    of  view,   much 

1  This  reminds  one  of  the  spread  of  Pebrinc  through  the  silkworms  ex- 
perimented on  by  Pasteur.  In  the  case  of  the  worms  the  organisms  first 
took  possession  of  the  intestinal  canal,  and  spread  thence  throughout  the 
body  of  the  worm.  See  p.  135  of  this  volume. 


PUTREFACTION   AND   INFECTION.  [31 

interest  attaches  to  Dr.  Klein's  remark  that  the  micro 
phyte,  which  he  describes  in  the  present  paper,  closely 
corresponds  with  that  which  Professor  Cohn,  the  eminent 
micro-botanist,  described,  under  the  name  of  Crenothrix 
polyspora,  as  found  by  him  "  in  the  well-water  of  a  certain 
district  in  Breslau,  famous  for  the  frequent  occurrence  of 
enteric  fever  among  its  inhabitants." ' 

Rarely  has  the  pen  of  a  medical  writer  produced 
a  paragraph  of  equal  importance  to  that  wherein  Mr. 
Simon  draws  a  distinction  between  the  fcetid  gases  and 
stinks  arising  from  animal  and  vegetable  putrefaction, 
and  the  real  contagia  concerned  in  the  production  and 
propagation  of  typhoid  fever.  'An  important  suggestion,' 
he  writes,  c  of  modern  science,  with  regard  to  the  nature 
of  the  operations  by  which  filth,  attacking  the  human 
body,  is  able  to  disorder  or  destroy  it,  is,  that  the  chief 
morbific  agencies  in  filth  are  other  than  those  chemically- 
identified  stinking  gaseous  products  of  organic  decomposi- 
tion which  force  themselves  on  popular  attention.1  Ex- 
posure to  the  sufficiently-concentrated  forms  of  organic 
decomposition  (as,  for  instance,  in  an  unventilated  old 
cesspool  or  long-blocked  sewer)  may,  no  doubt,  prove 
immediately  fatal,  by  reason  of  some  large  quantity  of 
sulphide  of  ammonium,  or  other  like  poisonous  and  fcetid 
gas,  which  the  sufferer  suddenly  inhales;  and  far  smaller 
doses  of  these  fcetid  gases  as  breathed  with  extreme  dilu- 
tion in  ordinary  stinking  atmospheres,  both  give  immediate 
headache  and  general  discomfort  to  sensitive  persons  tem- 
porarily exposed  to  them,  and  also  appear  to  keep  in  a 
somewhat  vaguely  depressed  state  of  health  many  who 
habitually  breathe  them:  but  here,  so  far  as  we  yet  know, 

1  Six  years  ago  I  -wrote  thus :  'Drains  and  cesspools,  indeed,  are  by  no 
means  in  such  evil  odour  as  they  used  to  be.  A  foetid  Thames  and  a  low- 
death-rate  occur  frcm  time  to  time  in  London.  For,  if  the  special  matter  or 
germs  of  epidemic  disorder  be  not  present,  a  corrupt  atmosphere,  however 
obnoxious  otherwise,  will  not  produce  the  disorder.'  See  p.  1 44  of  this  volume. 


82]  FRAGMENTS   OF   SCIENCE. 

is  the  end  of  the  potency  of  these  stinking  gases.  While, 
however,  thus  far  there  is  only  the  familiar  case  of  the  so- 
called  common  chemical  poison,  which  hurts  by  instant 
action  and  in  direct  proportion  to  its  palpable  and  ponder- 
able dose,  the  other  and  far  wider  possibilities  of  mischief 
which  we  recognise  in  filth  are  such  as  apparently  must 
be  attributed  to  morbific  ferments  or  contagia ;  matters 
which  not  only  are  not  gaseous,  but,  on  the  contrary,  so 
far  as  we  know  them,  seem  to  have  their  essence,  or  an 
inseparable  part  of  it,  in  certain  solid  elements  which  the 
microscope  discovers  in  them,  in  living  organisms,  namely, 
which  in  their  largest  sizes  are  but  very  minute  microsco- 
pical objects,  and  at  their  least  sizes  are  probably  unseen 
even  with  the  microscope  ;  organisms  -which,  in  virtue  of 
their  vitality,  are  indefinitely  self-multiplying  within 
their  respective  spheres  of  operation,  and  which,  therefore, 
as  in  contrast  with  common  poisons,  can  develop  indefi- 
nitely large  ulterior  effects  from  first  doses,  which  are  in- 
definitely small.1 

'  Of  ferments  thus  characterised,  the  apparently  essen- 
tial factors  of  specific  chemical  processes,  at  least  one 
sort — the  ordinary  septic  ferment — seems  always  to  be 
present  where  putrefactive  changes  are  in  progress,  as  of 
course  in  all  decaying  animal  refuse ;  while  others,  though 
certainly  not  essential  to  all  such  putridity,  are  in  dif- 
ferent degrees  apt,  and  some  of  them  little  less  than 
certain,  to  be  frequent  incidents  of  our  ordinary  re- 
fuse. As,  apparently,  it  is  by  these  various  agencies 
(essential  and  incidental)  that  filth  produces  "  zymotic  " 
disease,  it  is  important  not  to  confound  them  with  the 
fostid  gases  of  organic  decomposition ;  and  the  question, 
what  infecting  powers  are  prevalent  in  given  atmospheres 

1  See  the  parallel  case  of  the  infection  of  infusions  in  the  first  article  of 
this  volume,  p.  [23.  For  an  illustration  of  the  power  of  self -multi  plication 
in  •ilkwonns,  see  p.  139.  See  also  Lister,  p.  148 ;  also  pp.  171,  173. 


PUTREFACTION   AND    INFECTION.  [33 

should  never  be  regarded  as  a  mere  question  of  stink.  It 
is  of  the  utmost  practical  importance  to  recognise  in  regard 
of  filth,  that  agents  which  destroy  its  stink  may  yet  leave 
all  its  main  powers  of  disease-production  undiminished. 
Whether  the  ferments  of  disease,  if  they  could  be  isolated 
in  sufficient  quantity,  would  prove  themselves  in  any 
degree  odorous,  is  a  point  on  which  no  guess  need  be 
hazarded ;  but  it  is  certain  that  in  doses  in  which  they 
can  fatally  infect  the  human  body  they  are  infinitely  out 
of  reach  of  even  the  most  cultivated  sense  of  smell,  and 
that  this  sense  (though  its  positive  warnings  are  of  indis- 
pensable sanitary  service)  is  not  able,  except  by  indirect 
and  quite  insufficient  perceptions,  to  warn  us  against  risks 
of  morbid  infections. 

1  Even  as  regards  the  positive  notices  which  we  re- 
ceive by  the  sense  of  smell  with  regard  to  putrefactive 
decomposition,  we  must  not  assume  that  the  diffusion  and 
potency  of  septic  ferment  in  the  air  necessarily  go  pan 
passu  with  the  diffusion  and  offensiveness  of  the  foetid 
gases.  Witness,  on  a  very  large  scale,  the  experience 
of  London  in  the  summer  of  1858 ;  when,  as  persons 
who  were  then  frequenting  Westminster  may  well  re- 
member, our  tidal  river,  enormously  charged  with  de- 
composing sewage,  stank  week  after  week  in  a  degree 
which  excited  much  public  alarm  as  to  the  possible  con- 
sequences of  the  nuisance,  and  even  led  to  an  immediate 
interference  of  the  Legislature  ;  but  when,  though  the 
quantity  of  sulphuretted  hydrogen  in  the  river  atmopphere 
was  such  as  rapidly  to  blacken  the  ordinary  chemical  test- 
papers,  as  well  as  to  affect  in  the  same  way  the  lead-paint 
of  vessels  on  the  river,  and  was  enough  also  to  produce 
among  persons  much  engaged  on  the  river  such  signs  of 
sulphide-poisoning  as  I  have  above  mentioned,  the  par- 
ticular ailments  which  attest  the  working  of  septic  ferment 
on  the  human  body  were  in  even  less  than  average  preva 


84]  FRAGMENTS   OF   SCIENCE. 

lence  among  the  unwilling  subjects  of  this  large  experi- 
ment.' 

At  page  172  of  these  '  Fragments  '  I  use  the.  foil  owing 
language :  It  has  been  said,  and  it  is  sure  to  be  repeated, 
that  I  am  quitting  my  metier  in  speaking  of  these  things. 
Not  so.  I  am  dealing  with  questions  on  which  minds 
accustomed  to  weigh  the  value  of  experimental  evidence 
are  alone  competent  to  decide,  atfd  regarding  which  minds 
so  trained  are  as  capable  of  forming  a  correct  opinion  as 
they  are  regarding  a  problem  of  magnetism,  or  of  radiant 
heat.  'The  germ  theory  of  disease,'  it  has  been  said, 
'  appertains  to  the  biologist  and  the  physician  : '  granted ; 
but  not  to  them  alone ;  for  where  is  the  biologist  or 
physician  whose  researches  in  connection  with  this  sub- 
ject could  for  one  instant  be  compared  to  those  of  the 
chemist  Pasteur  ?  It  is  not  the  philosophic  members  of 
the  medical  profession  who  are  likely  to  be  dull  to  the 
reception  of  truth  because  it  does  not  originate  within 
the  pale  of  the  profession  itself. 

It  was  Dr.  Bastian  who  claimed  in  the  words  above 
quoted  the  germ  theory  of  disease  as  the  property  of  the 
biologist  and  the  physician.  For  six  years  his  claim  has 
been  conceded  to  him,  and  we  now  see  the  use  he  has 
made  of  the  concession.  But  I  regret  to  say,  that  the 
isame  view  of  the  subject  has  been  taken  by  other  very 
distinguished  men.  Sir  ^^rllliam  Jenner,  for  example,  in 
his  address  as  President  of  the  Clinical  Society,  employs 
the  following  language :  '  I  do  not  say,  nor  do  I  think, 
that  the  arguments  and  facts  able  to  be  adduced  in  favour 
of  the  origin  de  novo  of  the  contagious  diseases  are  con- 
clusive ;  but  I  do  say  they  are  strong  enough  to  make  us 
pause  before  we  accept  the  theory  advocated  by  Dr.  \Vm. 
Budd,  and  to  which  Professor  Tyndall  has  lent  the  weight 
of  his  name — a  weight  which  would,  however,  be  greater 
on  the  point  in  question  if  he  had  himself  studied  the  sub- 


PUTREFACTION   AND   INFECTION.  [35 

ject  on  which  he  has,  I  am  sorry  to  say,  addressed  the 
public  in  a  strain  calculated  to  check  unprejudiced  indi- 
vidual enquiry.' 

The  courtesy  of  Sir  William  Jenner's  reference  en- 
courages me  to  hope  that  he  will  accept  my  assurance 
that  the  part  I  have  publicly  taken  in  reference  to  Dr. 
Budd  was  preceded  by  no  small  amount  of  study  of  the 
question  in  hand.  Dr.  Murchison,  the  most  prominent 
leader  of  the  party  in  the  medical  profession  who  teach  the 
spontaneous  generation  of  infective  diseases,  affirms  that 
the  contagium  of  typhoid  fever  '  may  be  generated  inde- 
pendently of  a  previous  case  by  fermentation  of  fsecal  and 
perhaps  other  forms  of  organic  matter.'  I  think  it  prob- 
able that  the  experience  of  Sir  William  Jenner,  or  of  Dr. 
Murchison,  in  regard  to  fsecal  matter,  is  less  than  my  own. 
For  more  than  twenty  years  I  have  annually  had  occasion 
to  observe  fsecal  matter  of  all  kinds  seething  under  a 
summer  sun  in  the  villages,  hamlets,  and  chalets  of 
Switzerland,  and  proving  itself  utterly  incapable  of  gene- 
rating that  contagium  which,  according  to  Dr.  Murchison's 
teaching,  is  a  product  of  its  fermentation.  There  is  but 
one  way  of  getting  over  the  arguments  of  Dr.  Budd,  and 
that  is — to  destroy  his  facts :  for  these  being  granted,  his 
conclusions  are  irresistible.  To  his  facts  and  reasonings 
are  now  to  be  added  the  whole  weight  of  the  researches 
conducted  under  the  auspices  of  the  Privy  Council.  These 
are  dead  against  the  notion  favoured  by  Sir  William 
Jenner,  and  enunciated  by  Dr.  Murchison  as  one  of  the 
leading  conclusions  in  the  summary  of  his  learned  work  on 
'  Typhoid  Fever.'  I  may  be  permitted  to  express  a  doubt 
whether  in  England  a  dozen  years  hence  a  single  physician 
of  their  commanding  eminence  will  be  found  endorsing 
the  views  which  they  have  thought  it  their  duty  to 
enunciate  and  defend. 

At  the  end  of  this  volume  will  be  found,  with  a  few 


80]  FRAGMENTS   OF   SCIENCE. 

omissions  immaterial  to  the  principle  discussed,  the  letter 
to  the  *  Times '  which  provoked  at  the  time  of  its  publica- 
tion so  much  hostile  criticism,  and  brought  down  upon 
me  the  censure  of  Dr.  Murchison  and  Sir  William  Jenner. 
I  commit  it,  without  misgiving,  to  the  judgment  of  the 
future.  In  reference  to  my  allusion  to  Dr.  Klein,  Dr. 
Murchison,  at  a  meeting  of  the  Pathological  Society  on 
May  4,  1875,  spoke  thus:  '  I  believe  that  Dr.  Sanderson 
himself  would  be  the  first  to  repudiate  any  such  state- 
ment, and  I  think  that  any  one  who  has  listened  to  this 
debate  must  be  satisfied  that  such  an  announcement  was 
entirely  unwarranted  by  Dr.  Klein's  discovery  of  Bacteria 
iu  connection  with  the  lesions  of  enteric  fever.'  The 
reader  must  judge  between  Dr.  Murchison  and  me.  The 
warrant  for  my  reference  is  to  be  found  at  pp.  [29,  [30, 
and  [31,  where  Mr.  Simon's  account  of  Dr.  Klein's  dis- 
covery is  given  verbatim. 

I  take  this  opportunity  of  notifying  my  acceptance  of 
a  correction  on  a  point  of  history  at  the  hands  of  my 
eminent  opponent  the  Eeverend  Jatnes  Martineau.  It 
has  reference  to  a  passage  in  the  '  Belfast  Address,'  in 
which  the  relationship  of  Einpedocles  to  Democritus 
is  mentioned.  Speaking  of  a  passage  from  Lange,  Mr. 
Martineau  says :  *  Misled  by  the  order  of  this  passage, 
which  gives  the  missing  thought  after  naming  the  gap 
which  it  might  have  filled,  Dr.  Tyndall  has  described 
Empedocles  as  intentionally  making  good  a  defect  in 
Democritus.  This  is  an  inversion  of  the  chronology. 
Empedocles  preceded  Democritus  by  at  least  a  genera- 
tion, being  bora  about  B.G.  490  and  dying  B.C.  430 
whilst  Democritus,  whom  we  find  at  Thurii,  shortly  aftei 
the  foundation  of  the  colony,  in  B.C.  443,  died  at  a  very 
advanced  age  B.C.  357.'  A  reference  to  dates  in  Smith's 
'  Classical  Dictionary '  will  show  that  my  mistake  was  not 
an  unnatural  one. 


PAET  I. 


r. 

THE  CONSTITUTION  OF  NATURE* 

1806. 

WE  cannot  think  of  space  as  finite,  for  wherever  in 
imagination  we  erect  a  boundary,  we  are  compelled 
to  think  of  space  as  existing  beyond  it.  Thus  by  the 
incessant  dissolution  of  limits  we  arrive  at  a  more  or  less 
adequate  idea  of  the  infinity  of  space.  But,  though  com- 
pelled to  think  of  space  as  unbounded,  there  is  no  mental 
necessity  compelling  us  to  think  of  it  either  as  filled  or 
empty ;  whether  it  is  so  or  not  must  be  decided  by  ex- 
periment and  observation.  That  it  is  not  entirely  void,  the 
starry  heavens  declare  ;  but  the  question  still  remains,  Are 
the  stars  themselves  hung  in  vacuo  ?  Are  the  vast  regions 
which  surround  them,  and  across  which  their  light  is  pro- 
pagated, absolutely  empty  ?  A  century  ago  the  answer  to 
this  question  would  have  been,  '  No,  for  particles  of  light 
are  incessantly  shot  through  space.'  The  reply  of  modern 
science  is  also  negative,  but  on  different  grounds.  It  has 
the  best  possible  reasons  for  rejecting  the  idea  of  lumi- 
niferous  particles ;  but,  in  support  of  the  conclusion  that 
the  celestial  spaces  are  occupied  by  matter,  it  is  able  to 
offer  proofs  almost  as  cogent  as  those  which  can  be  adduced 

1  'Fortnightly  Review,'  vol.  iii.  p.  129. 


6  FEAGMENTS   OF   SCIENCE. 

for  the  existence  of  an  atmosphere  round  the  earth.  Men'g 
minds,  indeed,  rose  to  a  conception  of  the  celestial  and 
universal  atmosphere  through  the  study  of  the  terrestrial 
and  local  one.  From  the  phenomena  of  sound,  as  dis- 
played in  the  air,  they  ascended  to  the  phenomena  of  light, 
as  displayed  in  the  aether ;  which  is  the  name  given  to 
the  interstellar  medium. 

The  notion  of  this  medium  must  not  be  considered  as 
a  vague  or  fanciful  conception  on  the  part  of  scientific 
men.  Of  its  reality  most  cf  them  are  as  convinced  as 
they  are  of  the  existence  of  the  sun  and  moon.  The 
luminiferous  aether  has  definite  mechanical  properties.  It 
is  almost  infinitely  more  attenuated  than  any  known  gas, 
but  its  properties  are  those  of  a  solid  rather  than  of  a  gas. 
It  resembles  jelly  rather  than  air.  A  body  thus  consti- 
tuted may  have  its  boundaries  ;  but,  although  the  aether 
may  not  be  co-extensive  with  space,  it  must  at  all  events 
extend  as  far  as  the  most  distant  visible  stars.  In  fact  it 
is  the  vehicle  of  their  light,  and  without  it  they  could 
not  be  seen.  This  all-pervading  substance  takes  up  their 
molecular  tremors,  and  conveys  them  with  inconceivable 
rapidity  to  our  organs  of  vision.  It  is  the  transported 
shiver  of  bodies  countless  millions  of  miles  distant,  which 
translates  itself  in  human  consciousness  into  the  splendour 
of  the  firmament  at  night. 

If  the  aether  have  a  boundary,  masses  of  ponderable 
matter  might  be  conceived  to  exist  beyond  it,  but  they 
could  emit  no  light.  Beyond  the  aether  dark  suns  might 
burn  ;  there,  under  proper  conditions,  combustion  might 
be  carried  on  ;  fuel  might  consume  unseen,  and  metals  be 
fused  in  invisible  fires.  A  body,  moreover,  once  heated 
there,  would  continue  for  ever  heated  ;  a  sun  or  planet 
once  molten,  would  continue  for  ever  molten.  For,  the 
loss  of  heat  being  simply  the  abstraction  of  molecular 
motion  by  the  aether,  where  this  medium  is  absent  DO 


THE   CONSTITUTION   OF   NATURE.  6 

cooling  could  occur.  A  sentient  being  ou  approaching  a 
heated  body  in  this  region,  would  be  conscious  of  no 
augmentation  of  temperature.  The  gradations  of  warmth 
dependent  on  the  laws  of  radiation  would  not  exist,  and 
actual  contact  would  first  reveal  the  heat  of  an  extra 
aethereal  sun. 

Imagine  a  paddle-wheel  placed  in  water  and  caused  to 
rotate.  From  it,  as  a  centre,  waves  would  issue  in  all 
directions,  and  a  wader  as  he  approached  the  place  of 
disturbance  would  be  met  by  stronger  and  stronger  waves. 
This  gradual  augmentation  of  the  impression  made  upon 
the  wader's  body  is  exactly  analogous  to  the  augmentation 
of  light  when  we  approach  a  luminous  source.  In  the  one 
case,  however,  the  coarse  common  nerves  of  the  body 
suffice ;  for  the  other  we  must  have  the  finer  optic  nerve. 
But  suppose  the  water  withdrawn  ;  the  action  at  a  distance 
would  then  cease,  and,  as  far  as  the  sense  of  touch  is  con- 
cerned, the  wader  would  be  first  rendered  conscious  of  the 
motion  of  the  wheel  by  the  blow  of  the  paddles.  The 
transference  of  motion  from  the  paddles  to  the  water  is 
mechanically  similar  to  the  transference  of  molecular 
motion  from  the  heated  body  to  the  aether  ;  and  the  pro- 
pagation of  waves  through  the  liquid  is  mechanically 
similar  to  the  propagation  of  light  and  radiant  heat. 

As  far  as  our  knowledge  of  space  extends,  we  are  to 
conceive  it  as  the  holder  of  the  luminiferous  aether, 
through  which  are  interspersed,  at  enormous  distances 
apart,  the  ponderous  nuclei  of  the  stars.  Associated  with 
the  star  that  most  concerns  us  we  have  a  group  of  dark 
planetary  masses  revolving  at  various  distances  round  it, 
each  again  rotating  on  its  own  axis ;  and,  finally,  asso- 
ciated with  some  of  these  planets  we  have  dark  bodies  of 
minor  note — the  moons.  Whether  the  other  fixed  stars 
have  similar  planetary  companions  or  not  is  to  us  a 
matter  of  pure  conjecture,  which  may  or  may  not  entei 


6  FRAGMENTS   OF   SCIENCE. 

into  our  conception  of  the  universe.  But  probably  every 
thoughtful  person  believes,  with  regard  to  those  distant 
suns,  that  there  is,  in  space,  something  besides  our  system 
on  which  they  shine. 

From  this  general  view  of  the  present  condition  of 
space,  and  of  the  bodies  contained  in  it,  we  pass  to  the 
enquiry  whether  things  were  so  created  at  the  beginning. 
Was  space  furnished  at  once,  by  the  fiat  of  Omnipotence, 
with  these  burning  orbs  ?  To  this  question  the  man  of 
science,  if  he  confine  himself  within  his  own  limits,  will 
give  no  answer.  It  must,  however,  be  remarked  that  in 
the  formation  of  an  opinion  he  has  better  materials  to 
guide  him  than  anybody  else.  He  can  clearly  show  that 
the  present  state  of  things  may  be  derivative.  He  can 
even  assign  reasons  which  render  probable  its  derivative 
origin — that  it  was  not  originally  what  it  now  is.  At  all 
events,  he  can  prove  that  out  of  common  non-luminous 
matter  this  whole  pomp  of  stars  might  have  been  evolved. 

The  law  of  gravitation  enunciated  by  Newton  is,  that 
every  particle  of  matter  in  the  universe  attracts  every 
other  particle  with  a  force  which  diminishes  as  the  square 
of  the  distance  increases.  Thus  the  sun  and  the  earth 
mutually  pull  each  other ;  thus  the  earth  and  the  moon 
are  kept  in  company  ;  the  force  which  holds  every  re- 
spective pair  of  masses  together  being  the  integrated  force 
of  their  component  parts.  Under  the  operation  of  this 
force  a  stone  falls  to  the  ground  and  is  warmed  by  the 
shock ;  under  its  operation  meteors  plunge  into  our  atmo- 
sphere and  rise  to  incandescence.  Showers  of  such  doubt- 
less fall  incessantly  upon  the  sun.  Acted  on  by  this 
force,  were  it  stopped  in  its  orbit  to-morrow,  the  earth 
would  rush  towards,  and  finally  combine  with,  the  sun. 
Heat  would  also  be  developed  by  this  collision,  and  Mayer, 
Helmholtz,  and  Thomson  have  calculated  its  amount.  It 
would  equal  that  produced  by  the  combustion  of  more 


THE    CONSTITUTION   OF   NATURE.  7 

than  5,000  worlds  of  solid  coal,  all  this  heat  being  gene- 
rated at  the  instant  of  collision.  In  the  attraction  of 
gravity,  therefore,  acting  upon  non-luminous  matter,  we 
have  a  source  of  heat  more  powerful  than  could  be  derived 
from  any  terrestrial  combustion.  And  were  the  matter  of 
the  universe  thrown  in  cold  detached  fragments  into  space, 
and  there  abandoned  to  the  mutual  gravitation  of  its  own 
parts,  the  collision  of  the  fragments  would  in  the  end  pro- 
duce the  fires  of  the  stars. 

The  action  of  gravity  upon  matter  originally  cold  may, 
in  fact,  be  the  origin  of  all  light  and  heat,  and  also  the 
proximate  source  of  such  other  powers  as  are  generated  by 
light  and  heat.  But  we  have  now  to  enquire  what  is  the 
light  and  what  is  the  heat  thus  produced  ?  This  question 
has  already  been  answered  in  a  general  way.  Both  light 
and  heat  are  modes  of  motion.  Two  planets  clash  and  come 
to  rest;  their  motion,  considered  as  that  of  masses,  is 
destroyed,  but  it  is  really  continued  as  a  motion  of  their 
ultimate  particles.  It  is  this  latter  motion,  taken  up  by 
the  aether,  and  propagated  through  it  with  a  velocity  of 
186,000  miles  a  second,  that  comes  to  us  as  the  light  and 
heat  of  suns  and  stars.  The  atoms  of  a  hot  body  swing 
with  inconceivable  rapidity ;  but  this  power  of  vibration 
necessarily  implies  the  operation  of  forces  between  the 
atoms  themselves.  It  reveals  to  us  that  while  they  are 
held  together  by  one  force,  they  are  kept  asunder  by 
another,  their  position  at  any  moment  depending  on  the 
equilibrium  of  attraction  and  repulsion.  The  atoms  are 
virtually  connected  by  elastic  springs,  which  oppose  at 
the  same  time  their  approach  and  their  retreat,  but  which 
tolerate  the  vibration  called  heat.  The  molecular  vibration 
once  set  up  is  instantly  shared  with  the  aether,  and  diffused 
by  it  throughout  space. 

We  on  the  earth's  surface  live  night  and  day  in  the 
midst  of  aethereal  commotion.  The  medium  is  never  still. 


8  FRAGMENTS   OF   SCIENCE. 

The  cloud  canopy  above  us  may  be  thick  enough  to  shut 
out  the  light  of  the  stars  ;  but  this  canopy  is  itself  a  warm 
body,  which  radiates  its  motion  through  the  aether. 
The  earth  also  is  warm,  and  sends  its  heat-pulses  inces- 
santly forth.  It  is  the  waste  of  its  molecular  motion  in 
space  that  chills  the  earth  upon  a  clear  night ;  it  is  the 
return  of  its  motion  from  the  clouds  which  prevents  the 
earth's  temperature,  on  a  cloudy  night,  from  falling  so 
low.  To  the  conception  of  space  being  filled,  we  must 
therefore  add  the  conception  of  its  being  in  a  state  of 
incessant  tremor. 

The  sources  of  this  vibration  are  the  ponderable  masses 
of  the  universe.  Let  us  take  a  sample  of  these  and  ex- 
amine it  in  detail.  When  we  look  to  our  planet,  we  find 
it  to  be  an  aggregate  of  solids,  liquids,  and  gases.  When 
we  look  at  any  one  of  the^e,  we  generally  find  it  composed 
of  still  more  elementary  parts.  We  learn,  for  example, 
that  the  water  of  our  rivers  is  formed  by  the  union,  in 
definite  proportions,  of  two  gases,  oxygen  and  hydrogen. 
We  know  how  to  bring  these  constituents  together,  so  as 
to  form  water :  we  also  know  how  to  analyse  the  water, 
and  recover  from  it  its  two  constituents.  So,  likewise,  as 
regards  the  solid  proportions  of  the  earth.  Our  chalk 
hills,  for  example,  are  formed  by  a  combination  of  carbon, 
oxygen,  and  calcium.  These  are  elements  the  union  of 
which,  in  definite  proportions,  has  resulted  in  the  forma- 
tion of  chalk.  The  flints  within  the  chalk  we  know  to  be 
a  compound  of  oxygen  and  silicium,  called  silica  ;  and  our 
ordinary  clay  is,  for  the  most  part,  formed  by  the  union 
of  silicium,  oxygen,  and  the  well-known  light  metal,  alu- 
minium. By  far  the  greater  portion  of  the  earth's  crust 
is  compounded  of  the  elementary  substances  mentioned  in 
these  few  lines. 

The  principle  of  gravitation  has  been  already  described 
as  an  attraction  which  every  particle  of  matter,  however 


THE   CONSTITUTION   OF   NATURE.  8 

Email,  has  for  every  other  particle.  With  gravity  there 
is  no  selection ;  no  particular  atoms  choose,  by  pre- 
ference, other  particular  atoms  as  objects  of  attraction  ; 
the  attraction  of  gravitation  is  proportional  to  the  quan- 
tity of  the  attracting  matter,  regardless  of  its  quality. 
But  in  the  molecular  world  which  we  have  now  entered 
matters  are  otherwise  arranged.  Here  we  have  atoms 
between  which  a  strong  attraction  is  exercised,  and  also 
atoms  between  which  a  weak  attraction  is  exercised.  One 
atom  can  jostle  another  out  of  its  place,  in  virtue  of  a 
superior  force  of  attraction.  But,  though  the  amount  of 
force  exerted  varies  thus  from  atom  to  atom,  it  is  still 
an  attraction  of  the  same  mechanical  quality,  if  I  may 
use  the  term,  as  that  of  gravity  itself.  Its  intensity  might 
be  measured  in  the  same  way,  namely,  by  the  amount  of 
motion  which  it  can  generate  in  a  certain  time.  Thus  the 
attraction  of  gravity  at  the  earth's  surface  is  expressed 
by  the  number  82  ;  because,  when  acting  freely  on  a  body 
for  a  second  of  time,  it  imparts  to  the  body  a  velocity  of 
thirty-two  feet  a  second.  In  like  manner  the  mutual 
attraction  of  oxygen  and  hydrogen  might  be  measured 
by  the  velocity  imparted  to  the  atoms  in  their  rushing 
together.  Of  course,  such  a  unit  of  time  as  a  second  is 
not  here  to  be  thought  of,  the  whole  interval  required  by 
the  atoms  to  cross  the  minute  spaces  which  separate  them 
not  amounting  probably  to  more  than  an  inconceivably 
small  fraction  of  a  second. 

It  has  been  stated  that  when  a  body  falls  to  the  earth 
it  is  warmed  by  the  shock.  Here  we  have  what  we  may 
call  a  mechanical  combination  of  the  earth  and  the  body. 
Let  us  suffer  the  falling  body  and  the  earth  to  dwindle  in 
imagination  to  the  size  of  atoms,  and  for  the  attraction 
of  gravity  let  us  substitute  that  of  chemical  affinity ;  we 
have  then  what  is  called  a  chemical  combination.  The 
effect  of  the  union  in  this  case  also  is  the  development  of 


10  FRAGMENTS   OP   SCIENCE. 

heat,  and  from  the  amount  of  heat  generated  we  can  infer 
the  intensity  of  the  atomic  pull.  Measured  by  ordinary 
mechanical  standards,  this  is  enormous.  Mix  eight  pounds 
of  oxygen  with  one  of  hydrogen,  and  pass  a  spark  through 
the  mixture ;  the  gases  instantly  combine,  their  atoms 
rushing  over  the  little  distances  between  them.  Take  a 
weight  of  47,000  pounds  to  an  elevation  of  1,000  feet 
above  the  earth's  surface,  and  let  it  fall ;  the  energy  with 
which  it  will  strike  the  earth  will  not  exceed  that  of  the 
eight  pounds  of  oxygen  atoms,  as  they  dash  against  one 
pound  of  hydrogen  atoms  to  form  water. 

It  is  sometimes  stated  that  gravity  is  distinguished 
from  all  other  forces  by  the  fact  of  its  resisting  conversion 
into  other  forms  of  force.  Chemical  affinity,  it  is  said, 
can  be  converted  into  heat  and  light,  and  these  again  into 
magnetism  and  electricity :  but  gravity  refuses  to  be  so 
converted ;  being  a  force  maintaining  itself  under  all 
circumstances,  and  not  capable  of  disappearing  to  give 
place  to  another.  If  by  this  be  meant  that  a  particle  of 
matter  can  never  be  deprived  of  its  weight,  the  assertion 
is  correct ;  but  the  law  which  affirms  the  convertibility 
of  natural  forces  was  never  intended,  in  the  minds  of  those 
who  understood  it,  to  affirm  that  such  a  conversion  as  that 
here  implied  occurs  in  any  case  whatever.  As  regards 
convertibility  into  heat,  gravity  and  chemical  affinity 
stand  on  precisely  the  same  footing.  The  attraction  in 
the  one  case  is  as  indestructible  as  in  the  other.  Nobody 
affirms  that  when  a  stone  rests  upon  the  surface  of  the 
earth,  the  mutual  attraction  of  the  earth  and  stone  is 
abolished ;  nobody  means  to  affirm  that  the  mutual 
attraction  of  oxygen  for  hydrogen  ceases,  after  the  atoms 
have  combined  to  form  water.  What  is  meant,  in  the 
case  of  chemical  affinity,  is,  that  the  pull  of  that  affinity, 
acting  through  a  certain  space,  imparts  a  motion  of  trans- 
lation of  the  one  atom  towards  the  other.  This  motion 


THE   CONSTITUTION   OF  NATURE.  11 

is  not  heat,  nor  is  the  force  that  produces  it  heat. 
But  when  the  atoms  strike  and  recoil,  the  motion 
of  translation  is  converted  into  a  motion  of  vibration, 
which  is  heat.  The  vibration,  however,  so  far  from 
causing  the  extinction  of  the  original  attraction,  is  in 
part  carried  on  by  that  attraction.  The  atoms  recoil,  in 
virtue  of  the  elastic  force  which  opposes  actual  contact, 
and  in  the  recoil  they  are  driven  too  far  back.  The 
original  attraction  then  triumphs  over  the  force  of  recoil, 
and  urges  the  atoms  once  more  together.  Thus,  like  a 
pendulum,  they  oscillate,  until  their  motion  is  imparted 
to  the  surrounding  aether ;  or,  in  other  words,  until  their 
heat  becomes  radiant  heat. 

In  this  sense,  and  in  this  sense  only,  is  chemical 
affinity  converted  into  heat.  There  is,  first  of  all,  the 
attraction  between  the  atoms;  there  is,  secondly,  space 
between  them.  Across  this  space  the  attraction  urges 
them.  They  collide,  they  recoil,  they  oscillate.  There 
is  here  a  change  in  the  form  of  the  motion,  but  there  is 
no  real  loss.  It  is  so  with  the  attraction  of  gravity.  To 
produce  motion  by  gravity  space  must  also  intervene 
between  the  attracting  bodies  :  when  they  strike  together 
motion  is  apparently  destroyed,  but  in  reality  there  is  no 
destruction.  Their  atoms  are  suddenly  urged  together 
by  the  shock  ;  by  their  own  perfect  elasticity  these  atoms 
recoil ;  and  thus  is  set  up  the  molecular  oscillation  which 
announces  itself  to  the  nerves  as  heat. 

It  was  formerly  universally  supposed  that  by  the  colli- 
sion of  unelastic  bodies  force  was  destroyed.  Men  saw, 
for  example,  that  when  two  spheres  of  clay,  painter's 
putty,  or  lead,  were  urged  together,  the  motion  possessed 
by  the  masses,  prior  to  impact,  was  more  or  less  anni- 
hilated. They  believed  in  an  absolute  destruction  of  the 
force  of  impact.  Until  recent  times,  indeed,  no  difficulty 
was  experienced  in  believing  this,  whereas,  at  present, 


12  FRAGMENTS   OP   SCIENCE. 

the  ideas  of  force  and  its  destruction  refuse  to  be  united 
in  most  philosophic  minds.  In  the  collision  of  elastic 
bodies,  on  the  contrary,  it  was  observed  that  the  motion 
with  which  they  clashed  together  was  in  great  part  re- 
stored by  the  resiliency  of  the  masses,  the  more  perfect 
the  elasticity  the  more  complete  being  the  restitution. 
This  led  to  the  idea  of  perfectly  elastic  bodies — bodies 
competent  to  restore  by  their  recoil  the  whole  of  the 
motion  which  they  possessed  before  impact. 

Hence  arose  the  idea  of  the  conservation  of  force,  as 
opposed  to  that  destruction  of  force  which  was  supposed 
to  occur  when  unelastic  bodies  met  in  collision. 

"We  now  know  that  the  principle  of  conservation  holds 
equally  good  with  elastic  and  unelastic  bodies.  Perfectly 
elastic  bodies  develop  no  heat  on  collision.  They  retain 
their  motion  afterwards,  though  its  direction  may  be 
changed ;  and  it  is  only  when  sensible  motion  is  wholly 
or  partly  destroyed,  that  heat  is  generated.  This  always 
occurs  in  unelastic  collision,  the  heat  developed  being  the 
exact  equivalent  of  the  sensible  motion  extinguished. 
This  heat  virtually  declares  that  the  property  of  elasticity, 
denied  to  the  masses,  exists  among  their  atoms ;  and  by 
the  recoil  and  oscillation  of  these  the  principle  of  conser- 
vation is  vindicated. 

But  ambiguity  in  the  use  of  the  term  '  force '  has 
ueen  for  some  time  more  and  more  making  itself  felt. 
We  called  the  attraction  of  gravity  a  force,  without  any 
reference  to  motion.  A  body  resting  on  a  shelf  is  as 
much  pulled  by  gravity  as  when,  after  having  been  pushed 
off  the  shelf,  it  falls  towards  the  earth.  We  applied  the 
term  force  also  to  that  molecular  attraction  which  we 
called  chemical  affinity.  When,  however,  we  spoke  of 
the  conservation  of  force,  in  the  case  of  elastic  collision, 
we  meant  neither  a  pull  nor  a  push,  which,  as  just  in- 
dicated, might  be  exerted  upon  inert  matter,  but  we 


THE   CONSTITUTION   OF   NATUEE.  13 

meant  the  moving  force,  if  I  may  use  the  term,  of  the 
colliding  masses. 

What  I  have  called  moving  force  has  a  definite  me- 
chanical measure,  in  the  amount  of  work  that  it  can 
perform.  The  simplest  form  of  work  is  the  raising  of  a 
weight.  A  man  walking  up-hill,  or  up-stairs,  with  a 
pound  weight  in  his  hand,  to  an  elevation  say  of  sixteen 
feet,  performs  a  certain  amount  of  work,  over  and  above 
the  lifting  of  his  own  body.  If  he  ascend  to  a  height  of 
thirty-two  feet,  he  does  twice  the  work ;  if  to  a  height  of 
forty-eight  feet,  he  does  three  times  the  work ;  if  to 
sixty-four  feet  he  does  four  times  the  work,  and  so  on. 
If,  moreover,  he  carries  up  two  pounds  instead  of  one, 
other  things  being  equal,  he  does  twice  the  work;  if 
three,  four,  or  five  pounds,  he  does  three,  four,  or  five 
times  the  work.  In  fact  it  is  plain  that  the  work  per- 
formed depends  on  two  factors,  the  weight  raised  and  the 
height  to  which  it  is  raised.  It  is  expressed  by  the  pro- 
duct of  these  two  factors. 

But  a  body  may  be  caused  to  reach  a  certain  elevation 
in  opposition  to  the  force  of  gravity,  without  being  actually 
carried  up  to  that  elevation.  If  a  hodman,  for  example, 
wished  to  land  a  brick  at  an  elevation  of  sixteen  feet 
above  the  place  where  he  stood,  he  would  probably  pitch 
it  up  to  the  bricklayer.  He  would  thus  impart,  by  a 
sudden  effort,  a  velocity  to  the  brick  sufficient  to  raise  it 
to  the  required  height ;  the  work  accomplished  by  that 
effort  being  precisely  the  same  as  if  he  had  slowly  carried 
up  the  brick.  The  initial  velocity  to  be  imparted,  in  this 
case,  is  well  known.  To  reach  a  height  of  sixteen  feet, 
the  brick  must  quit  the  man's  hand  with  a  velocity  of 
thirty-two  feet  a  second.  It  is  needless  to  say,  that  a 
body  starting  with  any  velocity,  would,  if  wholly  unop- 
posed or  unaided,  continue  to  move  for  ever  with  the 
same  velocity.  But  when,  as  in  the  case  before  us,  the 


14  FRAGMENTS   OF   SCIENCE. 

body  is  thrown  upwards,  it  moves  in  opposition  to  gravity, 
which  incessantly  retards  its  motion,  and  finally  brings  it 
to  rest  at  an  elevation  of  sixteen  feet.  If  not  here  caught 
by  the  bricklayer,  it  would  return  to  the  hodman  with  an 
accelerated  motion,  and  reach  his  hand  with  the  precise 
velocity  it  possessed  on  quitting  it. 

Supposing  the  man  competent  to  impart  to  the  brick, 
at  starting,  a  speed  of  sixty-four  feet  a  second,  or  twice 
its  former  speed,  would  the  amount  of  work  performed  in 
this  effort  be  only  twice  what  it  was  in  the  first  instance  ? 
No;  it  would  be  four  times  that  quantity.  A  body 
starting  with  twice  the  velocity  of  another,  will  rise  to 
four  times  the  height ;  in  like  manner,  a  three-fold 
velocity  will  give  a  nine- fold  elevation,  a  four-fold  velocity 
will  give  a  sixteen-fold  elevation,  and  so  on.  The  height 
attained,  then,  or  the  work  done,  is  not  proportional 
to  the  velocity,  but  to  the  square  of  the  velocity.  As 
before,  the  work  is  also  proportional  to  the  weight 
elevated.  Hence  the  work  which  any  moving  mass 
whatever  is  competent  to  perform,  by  the  motion  which 
it  at  any  moment  possesses,  is  jointly  proportional  to 
its  weight  and  the  square  of  its  velocity.  Here,  then, 
we  have  a  second  measure  of  work,  in  which  we  simply 
translate  the  idea  of  height  into  its  equivalent  idea  of 
motion. 

In  mechanics,  the  product  of  the  mass  of  a  moving 
body  into  the  square  of  its  velocity,  expresses  what  is 
called  the  via  viva,  or  living  force.  It  is  also  sometimes 
called  the  '  mechanical  effect.'  If,  for  example,  a  cannon 
pointed  to  the  zenith  urge  a  ball  upwards  with  twice  the 
velocity  imparted  to  a  second  ball,  the  former  will  rise  to 
four  times  the  height  attained  by  the  latter.  If  directed 
against  a  target,  it  will  also  do  four  times  the  execu- 
tion. Hence  the  importance  of  imparting  a  high  velocity 
to  projectiles  in  war.  Having  thus  cleared  our  way  to  a 


THE   CONSTITUTION  OP  NATURE.  15 

perfectly  definite  conception  of  the  via  viva  of  moving 
masses,  we  are  prepared  for  the  announcement  that  the 
heat  generated  by  the  shock  of  a  falling  body  against  the 
earth  is  proportional  to  the  via  viva  annihilated.  In 
point  of  fact,  it  is  not  an  annihilation  at  all,  but  a  trans- 
ference of  vis  viva  from  the  mass  to  its  ultimate  particles. 
This,  as  we  now  learn,  is  proportional  to  the  square  of 
the  velocity.  In  the  case,  therefore,  of  two  cannon-balls 
of  equal  weight,  if  one  strike  a  target  with  twice  the 
velocity  of  the  other,  it  will  generate  four  times  the  heat ; 
if  with  three  times  the  velocity,  it  will  generate  nine  times 
the  heat,  and  so  on. 

Mr.  Joule  has  shown  that  in  falling  from  a  height  of 
772  feet,  a  body  will  generate  an  amount  of  heat  sufficient 
to  raise  its  own  weight  of  water  one  degree  Fahrenheit 
in  temperature.  We  have  here  the  mechanical  equivalent 
of  heat.  Now,  a  body  falling  from  a  height  of  772  feet, 
has,  upon  striking  the  earth,  a  velocity  of  223  feet  a 
second  ;  and  if  this  velocity  were  imparted  to  a  body,  by 
any  other  means,  the  quantity  of  heat  generated  by  the 
stoppage  of  its  motion  would  be  that  stated  above.  Six 
times  that  velocity,  or  1,338  feet,  would  not  be  an  in- 
ordinate one  for  a  cannon-ball  as  it  quits  the  gun.  Hence, 
a  cannon-ball  moving  with  a  velocity  of  1,338  feet  a  second, 
would,  by  collision,  generate  an  amount  of  heat  competent 
to  raise  its  own  weight  of  water  36  degrees  Fahrenheit  in 
temperature.  If  composed  of  iron,  and  if  all  the  heat 
generated  were  concentrated  in  the  ball  itself,  its  tempe- 
rature would  be  raised  about  360  degrees  Fahrenheit ; 
because  one  degree  in  the  case  of  water  is  equivalent  to 
about  ten  degrees  in  the  case  of  iron.  In  artillery  prac- 
tice, the  heat  generated  is  usually  concentrated  upon  the 
front  of  the  bolt,  and  on  the  portion  of  the  target  first 
struck.  By  this  concentration  the  heat  developed  be- 
comes sufficiently  intense  to  raise  the  dust  of  the  metal 


10  FRAGMENTS    OF    SCIENCE. 

to  incandescence,  a  flash  of  light  often  accompanying 
collision  with  the  target. 

Let  us  now  fix  our  attention  for  a  moment  on  the 
gunpowder  which  urges  the  cannon-ball.  This  is  com- 
posed of  combustible  matter,  which  if  burnt  in  the  open 
air  would  yield  a  certain  amount  of  heat.  It  will  not 
yield  this  amount  if  it  perform  the  work  of  urging  a 
ball.  The  heat  then  generated  by  the  gunpowder  will 
fall  short  of  that  produced  in  the  open  air,  by  an  amount 
equivalent  to  the  via  viva  of  the  ball ;  and  this  exact 
amount  is  restored  by  the  ball  on  its  collision  with  the 
target.  In  this  perfect  way  are  heat  and  mechanical 
motion  connected. 

Broadly  enunciated,  the  principle  of  the  consexvation 
of  force  asserts,  that  the  quantity  of  force  in  the  uni- 
verse is  as  unalterable  as  the  quantity  of  matter ;  that 
it  is  alike  impossible  to  create  force  and  to  annihilate  it. 
But  in  what  sense  are  we  to  understand  this  assertion  ? 
It  would  be  manifestly  inapplicable  to  the  force  of  gravity 
as  defined  by  Newton  ;  for  this  is  a  force  varying  inversely 
as  the  square  of  the  distance ;  and  to  affirm  the  con- 
stancy of  a  varying  force  would  be  self-contradictory. 
Yet,  when  the  question  is  properly  understood,  gravity 
forms  no  exception  to  the  law  of  conservation.  Follow- 
ing the  method  pursued  by  Helmholtz,  I  will  here  at- 
tempt an  elementary  exposition  of  this  law.  Though 
destined  in  its  applications  to  produce  momentous 
changes  in  human  thought,  it  is  not  difficult  of  compre- 
hension. 

For  the  sake  of  simplicity  we  will  consider  a  particle 
of  matter,  which  we  may  call  F,  to  be  perfectly  fixed, 
and  a  second  movable  particle,  p,  placed  at  a  distance 
from  F.  We  will  assume  that  these  two  particles  attract 
each  other  according  to  the  Newtonian  law.  At  a  certain 
distance,  the  attraction  is  of  a  certain  definite  amount, 


THE   CONSTITUTION   OP   NATURE.  17 

which  might  be  determined  by  means  of  a  spring  balance. 
At  half  this  distance  the  attraction  would  be  augmented 
four  times ;  at  a  third  of  the  distance,  nine  times ;  at 
one-fourth  of  the  distance,  sixteen  times,  and  so  on.  In 
every  case,  the  attraction  might  be  measured  by  deter- 
mining, with  the  spring  balance,  the  amount  of  tension 
just  sufficient  to  prevent  D  from  moving  towards  r. 
Thus  far  we  have  nothing  whatever  to  do  with  motion  ; 
we  deal  with  statics,  not  with  dynamics.  We  simply 
take  into  account  the  distance  of  D  from  F,  and  the  pull 
exerted  by  gravity  at  that  distance. 

It  is  customary  in  mechanics  to  represent  the  magni- 
tude of  a  force  by  a  line  of  a  certain  length,  a  force  of 
double  magnitude  being  represented  by  a  line  of  double 
length,  and  so  on.  Placing  then  the  particle  D  at  a  dis- 
tance from  F,  we  can,  in  imagination,  draw  a  straight 
line  from  D  to  F,  and  at  i»  erect  a  perpendicular  to  this 
line,  which  shall  represent  the  amount  of  the  attraction 
exerted  on  D.  If  D  be  at  a  very  great  distance  from  F,  the 
attraction  will  be  very  small,  and  the  perpendicular  conse- 
quently very  short.  If  the  distance  be  practically  infinite, 
the  attraction  is  practically  m£.  Let  us  now  suppose  at  every 
point  in  the  line  joining  F  and  D  a  perpendicular  to  be 
erected,  proportional  in  length  to  the  attraction  exerted 
at  that  point ;  we  thus  obtain  an  infinite  number  of 
perpendiculars,  of  gradually  increasing  length,  as  D  ap- 
proaches F.  Uniting  the  ends  of  all  these  perpendiculars, 
we  obtain  a  curve,  and  between  this  curve  and  the  straight 
line  joining  F  and  D  we  have  an  area  containing  all  the 
perpendiculars  placed  side  by  side.  Each  one  of  this 
infinite  series  of  perpendiculars  representing  an  attraction, 
or  tension,  as  it  is  sometimes  called,  the  area  just  referred 
to  represents  the  total  effort  capable  of  being  exerted  by 
the  tensions,  upon  the  particle  D,  during  its  passage  from 
its  first  position  to  F. 


18  FRAGMENTS   OP   SCIENCE. 

Up  to  the  present  point  we  have  been  dealing  with 
tensions,  not  with  motion.  Thus  far  vis  viva  has  been 
entirely  foreign  to  our  contemplation  of  D  and  F.  Let  us 
now  suppose  D  placed  at  a  practically  infinite  distance 
from  F  ;  here,  as  stated,  the  pull  of  gravity  would  be 
nothing,  and  the  perpendicular  representing  it  would 
dwindle  to  a  point.  In  this  position  the  sum  of  the 
tensions  capable  of  being  exerted  on  D  would  be  a  maxi- 
mum. Let  D  now  begin  to  move  in  obedience  to  the  at- 
traction exerted  upon  it.  Motion  being  once  set  up,  the 
idea  of  vis  viva  arises.  In  moving  towards  F  the  particle 
D  consumes  as  it  were,  the  tensions.  Let  us  fix  our  at- 
tention on  D,  at  any  point  of  the  path  over  which  it  is 
moving.  Between  that  point  and  F  there  is  a  quantity  of 
unused  tensions ;  beyond  that  point  the  tensions  have 
been  all  consumed,  but  we  have  in  their  place  an  equiva- 
lent quantity  of  vis  viva.  After  i>  has  passed  any  point, 
the  tension  previously  in  store  at  that  point  disappears, 
but  not  without  having  added,  during  the  infinitely  small 
duration  of  its  action,  a  due  amount  of  motion  to  that 
previously  possessed  by  D.  The  nearer  D  approaches  to  F, 
the  smaller  is  the  sum  of  the  tensions  remaining,  but  the 
greater  is  the  living  force ;  the  farther  D  is  from  F,  the 
greater  is  the  sum  of  the  unconsumed  tensions,  and  the 
less  is  the  living  force.  Now  the  principal  of  conservation 
affirms  not  the  constancy  of  the  value  of  the  tensions  of 
gravity,  nor  yet  the  constancy  of  the  vis  viva,  taken 
separately,  but  the  absolute  constancy  of  the  value  of  the 
sum  of  both.  At  the  beginning  the  vis  viva  was  zero, 
and  the  tension  area  was  a  maximum ;  close  to  ¥  the  vis 
viva  is  a  maximum,  while  the  tension  area  is  zero.  At 
every  other  point,  the  work-producing  power  of  the  particle 
D  consists  in  part  of  vis  viva,  and  in  part  of  tensions. 

If  gravity,  instead  of  being  attraction,  were  repulsion, 
then,  with  the  particles  in  contact,  the  sum  of  the  tensions 


THE   CONSTITUTION   OF   NATURE.  19 

between  D  and  r  would  be  a  maximum,  and  the  via  viva 
zero.  If,  in  obedience  to  the  repulsion,  D  moved  away 
from  r,  vis  viva  would  be  generated ;  and  the  farther  D 
retreated  from  F  the  greater  would  be  its  vis  viva,  and 
the  less  the  amount  of  tension  still  available  for  producing 
motion.  Taking  repulsion  as  well  as  attraction  into 
account,  the  principle  of  the  conservation  of  force  affirms 
that  the  mechanical  value  of  the  tensions  and  vires  vivce 
of  the  material  universe,  so  far  as  we  know  it,  is  a  constant 
quantity.  The  universe,  in  short,  possesses  two  kinds  of 
property  which  are  mutually  convertible  at  an  unvarying 
rate.  The  diminution  of  either  carries  with  it  the  en- 
hancement of  the  other,  the  total  value  of  the  property 
remaining  unchanged. 

The  considerations  here  applied  to  gravity  apply 
equally  to  chemical  affinity.  In  a  mixture  of  oxygen  and 
hydrogen  the  atoms  exist  apart,  but  by  the  application  of 
proper  means  they  may  be  caused  to  rush  together  across 
the  space  that  separates  them.  While  this  space  exists, 
and  as  long  as  the  atoms  have  not  begun  to  move  towards 
each  other,  we  have  tensions  and  nothing  else.  During 
their  motion  towards  each  other  the  tensions,  as  in  the 
case  of  gravity,  are  converted  into  vis  viva.  After  they 
clash  we  have  still  vis  viva,  but  in  another  form.  It  was 
translation,  it  is  vibration.  It  was  molecular  transfer,  it 
is  heat. 

It  is  possible  to  reverse  these  processes,  to  unlock  the 
embrace  of  the  atoms  and  replace  them  in  their  first 
positions.  But,  to  accomplish  this,  as  much  heat  would  be 
required  as  was  generated  by  their  union.  Such  reversals 
occur  daily  and  hourly  in  nature.  By  the  solar  waves,  the 
oxygen  of  water  is  divorced  from  its  hydrogen  in  the 
leaves  of  plants.  As  molecular  vis  viva  the  waves  dis- 
appear, but  in  so  doing  they  re-endow  the  atoms  of  oxygen 
and  hydrogen  with  tension.  The  atoms  are  thus  enabled 


20  FRAGMENTS   OF   SCIENCE. 

to  recombine,  and  when  tbey  do  so  they  restore  the 
precise  amount  of  heat  consumed  in  their  separation. 
The  same  remarks  apply  to  the  compound  of  carbon  and 
oxygen,  called  carbonic  acid,  which  is  exhaled  from  our 
lungs,  produced  by  our  fires,  and  found  sparingly  diffused 
everywhere  throughout  the  air.  In  the  leaves  of  plants 
the  sunbeams  also  wrench  the  atoms  of  carbonic  acid 
asunder,  and  sacrifice  themselves  in  the  act ;  but  when 
the  plants  are  burnt,  the  amount  of  heat  consumed  in 
their  production  is  restored. 

This,  then,  is  the  rhythmic  play  of  Nature  as  regards 
her  forces.  Throughout  all  her  regions  she  oscillates  from 
tension  to  vis  viva,  from  vis  viva  to  tension.  We  have 
the  same  play  in  the  planetary  system.  The  earth's  orbit 
is  an  ellipse,  one  of  the  foci  of  which  is  occupied  by  the 
sun.  Imagine  the  earth  at  the  most  distant  part  of  the 
orbit.  Her  motion,  and  consequently  her  vis  viva,  is  then 
a  minimum.  The  planet  rounds  the  curve,  and  begins  its 
approach  to  the  sun.  In  front  it  has  a  store  of  tensions, 
which  is  gradually  consumed,  an  equivalent  amount  of 
vis  viva  being  generated.  When  nearest  to  the  sun  the 
motion,  and  consequently  the  vis  viva,  reach  a  maximum. 
But  here  the  available  tensions  have  been  used  up.  The 
earth  rounds  this  portion  of  the  curve  and  retreats  from 
the  sun.  Tensions  are  now  stored  up,  but  vis  viva  is 
lost,  to  be  again  restored  at  the  expense  of  the  comple- 
mentary force  on  the  opposite  side  of  the  curve.  Thus 
beats  the  heart  of  the  universe,  but  without  increase  or 
diminution  of  its  total  stock  of  force. 

I  have  thus  far  tried  to  steer  clear  amid  confusion,  by 
fixing  the  mind  of  the  reader  upon  things  rather  than 
upon  names.  But  good  names  are  essential ;  and  here, 
as  yet,  we  are  not  provided  with  such.  We  have  had  the 
force  of  gravity  and  living  force — two  utterly  distinct 
things.  We  have  had  pulls  and  tensions ;  and  we  might 


THE   CONSTITUTION   OF   NATURE.  21 

have  had  the  force  of  heat,  the  force  of  light,  the  force  of 
magnetism,  or  the  force  of  electricity — all  of  which  terms 
have  been  employed  more  or  less  loosely  by  writers  on 
physics.  This  confusion  is  happily  avoided  by  the  intro- 
duction of  the  term  '  energy,'  which  embraces  both  tension 
and  vis  viva.  Energy  is  possessed  by  bodies  already  in 
motion ;  it  is  then  actual,  and  we  agree  to  call  it  actual 
or  dynamic  energy.  It  is  our  old  vis  viva.  On  the 
other  hand,  energy  is  possible  to  bodies  not  in  motion, 
but  which,  in  virtue  of  attraction  or  repulsion,  possess  a 
power  of  motion  which  would  realise  itself  if  all  hindrances 
were  removed.  Looking,  for  example,  at  gravity ;  a  body 
on  the  earth's  surface  in  a  position  from  which  it  cannot 
fall  to  a  lower  one  possesses  no  energy.  It  has  neither 
motion  nor  power  of  motion.  But  the  same  body  sus- 
pended at  a  height  above  the  earth  has  a  power  of  motion, 
though  it  may  not  have  exercised  it.  Energy  is  possible 
to  such  a  body,  and  we  agree  to  call  this  potential  energy. 
It  consists  of  our  old  tensions.  We,  moreover,  speak  of 
the  conservation  of  energy,  instead  of  the  conservation  of 
force  ;  and  say  that  the  sum  of  the  potential  and  dynamic 
energies  of  the  material  universe  is  a  constant  quantity. 

A  body  cast  upwards  consumes  the  actual  energy  of 
projection,  and  lays  up  potential  energy.  When  it  reaches 
its  utmost  height  all  its  actual  energy  is  consumed,  its 
potential  energy  being  then  a  maximum.  When  it 
returns,  there  is  a  reconversion  of  the  potential  into  the 
actual.  A  pendulum  at  the  limit  of  its  swing  possesses 
potential  energy ;  at  the  lowest  point  of  its  arc  its  energy 
is  all  actual.  A  patch  of  snow  resting  on  a  mountain 
slope  has  potential  energy ;  loosened,  and  shooting  down 
as  an  avalanche,  it  possesses  dynamic  energy.  The  pine- 
trees  growing  on  the  Alps  have  potential  energy;  but 
rushing  down  the  Holznnne  of  the  woodcutters  they 
possess  actual  energy.  The  same  is  true  of  the  mountains 


22  FRAGMENTS   OF   SCIENCE. 

themselves.  As  long  as  the  rocks  which  compose  them 
can  fall  to  a  lower  level,  they  possess  potential  energy, 
which  is  converted  into  actual  when  the  frost  ruptures 
their  cohesion  and  hands  them  over  to  the  action  of 
gravity.  The  hammer  of  the  great  bell  of  Westminster, 
when  raised  before  striking,  possesses  potential  energy ; 
when  it  falls,  the  energy  becomes  dynamic  ;  and  after  the 
stroke,  we  have  the  rhythmic  play  of  potential  and  dynamic 
in  the  vibrations  of  the  bell.  The  same  holds  good  for 
the  molecular  oscillations  of  a  heated  body.  An  atom  is 
driven  against  its  neighbour,  and  recoils.  The  ultimate 
amplitude  of  the  recoil  being  attained,  the  motion  of  the 
atom  in  that  direction  is  checked,  and  for  an  instant  its 
energy  is  all  potential.  It  is  then  drawn  towards  its 
neighbour  with  accelerated  speed ;  thus,  by  attraction, 
converting  its  potential  into  dynamic  energy.  Its  motion 
in  this  direction  is  also  finally  checked,  and  again,  for  an 
instant,  its  energy  is  all  potential.  It  once  more  retreats, 
converting,  by  repulsion,  its  potential  into  dynamic  energy, 
till  the  latter  attains  a  maximum,  after  waich  it  is  again 
changed  into  potential  energy.  Thus,  what  is  true  of  the 
earth,  as  she  swings  to  and  fro  in  her  yearly  journey 
round  the  sun,  is  also  true  of  her  minutest  atom.  We 
have  wheels  within  wheels,  and  rhythm  within  rhythm. 

When  a  body  is  heated,  a  change  of  molecular  arrange- 
ment always  occurs,  and  to  produce  this  change-  heat  is 
consumed.  Hence,  a  portion  only  of  the  heat  communi- 
cated to  the  body  remains  as  dynamic  energy.  Looking 
back  on  some  of  the  statements  made  at  the  beginning  of 
this  article,  now  that  our  knowledge  is  more  extensive,  we 
see  the  necessity  of  qualifying  them.  When,  for  example, 
two  bodies  clash,  heat  is  generated ;  but  the  heat,  or  mole- 
cular dynamic  energy,  developed  at  the  moment  of  colli- 
sion, is  not  the  equivalent  of  the  sensible  dynamic  energy 
destroyed.  The  true  equivalent  is  this  heat,  plus  the 


THE   CONSTITUTION   OF   NATUKE.  23 

potential  energy  conferred  upon  the  molecules  by  the 
placing  of  greater  distances  between  them.  This  mole- 
cular potential  energy  is  afterwards,  on  the  cooling  of  the 
body,  converted  into  heat. 

Wherever  two  atoms  capable  of  uniting  together  by 
their  mutual  attractions  exist  separately,  they  form  a 
store  of  potential  energy.  Thus  our  woods,  forests,  and 
coal-fields  on  the  one  hand,  and  our  atmospheric  oxygen 
on  the  other,  constitute  a  vast  store  of  energy  of  this  kind 
— vast,  but  far  from  infinite.  We  have,  besides  our  coal- 
fields, metallic  bodies  more  or  less  sparsely  distributed 
through  the  earth's  crust.  These  bodies  can  be  oxydised ; 
and  hence  they  are,  so  far  as  they  go,  stores  of  potential 
energy.  But  the  attractions  of  the  great  mass  of  the 
earth's  crust  are  already  satisfied,  and  from  them  no  fur- 
ther energy  can  possibly  be  obtained.  Ages  ago  the  ele- 
mentary constituents  of  our  rocks  clashed  together  and 
produced  the  motion  of  heat,  which  was  taken  up  by  the 
aether  and  carried  away  through  stellar  space.  It  is  lost 
for  ever  as  far  as  we  are  concerned.  In  those  ages  the  hot 
conflict  of  carbon,  oxygen,  and  calcium  produced  the  chalk 
and  limestone  hills  which  are  now  cold ;  and  from  this 
carbon,  oxygen,  and  calcium  no  further  energy  can  be 
derived.  So  it  is  with  almost  all  the  other  constituents 
of  the  earth's  crust.  They  took  their  present  form  in 
obedience  to  molecular  force  ;  they  turned  their  potential 
energy  into  dynamic,  and  gave  it  to  the  universe,  ages 
before  man  appeared  upon  this  planet.  For  him  a  residue 
of  potential  energy  remains,  vast,  truly,  in  relation  to  the 
life  and  wants  of  an  individual,  but  exceedingly  minute  in 
comparison  with  the  earth's  primitive  store. 

To  sum  up.  The  whole  stock  of  energy  or  working- 
power  in  the  world  consists  of  attractions,  repulsions,  and 
motions.  If  the  attractions  and  repulsions  be  so  circum- 
stanced as  to  be  able  to  produce  motion,  they  are  sources 


24  FRAGMENTS   OF   SCIENCE. 

of  working-power,  but  not  otherwise.  As  stated  a  moment 
ago,  the  attraction  exerted  between  the  earth  and  a  body 
at  a  distance  from  the  earth's  surface,  is  a  source  of  work- 
ing-power ;  because  the  body  can  be  moved  by  the  attrac- 
tion, and  in  falling  to  the  earth  can  perform  work.  When 
it  rests  upon  the  earth's  surface  it  is  not  a  source  of  power 
or  energy,  because  it  can  fall  no  farther.  But  though  it 
has  ceased  to  be  a  source  of  energy,  the  attraction  of 
gravity  still  acts  as  a  force,  which  holds  the  earth  and 
weight  together. 

The  same  remarks  apply  to  attracting  atoms  and 
molecules.  As  long  as  distance  separates  them,  they  can 
move  across  it  in  obedience  to  the  attraction;  and  the 
motion  thus  produced  may,  by  proper  appliances,  be  caused 
to  perform  mechanical  work.  When,  for  example,  two 
atoms  of  hydrogen  unite  with  one  of  oxygen,  to  form 
water,  the  atoms  are  first  drawn  towards  each  other — 
they  move,  they  clash,  and  then  by  virtue  of  their  re- 
siliency, they  recoil  and  quiver.  To  this  quivering  motion 
we  give  the  name  of  heat.  This  atomic  vibration  is  merely 
the  redistribution  of  the  motion  produced  by  the  chemical 
affinity;  and  this  is  the  only  sense  in  which  chemical 
affinity  can  be  said  to  be  converted  into  heat.  We  must 
not  imagine  the  chemical  attraction  destroyed,  or  con- 
verted into  anything  else.  For  the  atoms,  when  mutually 
clasped  to  form  a  molecule  of  water,  are  held  together  by 
the  very  attraction  which  first  drew  them  towards  each 
other.  That  which  has  really  been  expended  is  the  pull 
exerted  through  the  space  by  which  the  distance  between 
the  atoms  has  been  diminished. 

If  this  be  understood,  it  will  be  at  once  seen  that 
gravity  may,  in  this  sense,  be  said  to  be  convertible  into 
heat ;  that  it  is  in  reality  no  more  an  outstanding  and 
inconvertible  agent,  as  it  is  sometimes  stated  to  be,  than 
is  chemical  affinity.  By  the  exertion  of  a  certain  pull 


THE   CONSTITUTION   OF   NATURE.  25 

through  a  certain  space,  a  body  is  caused  to  clash  with 
a  certain  definite  velocity  against  the  earth.  Heat  is 
thereby  developed,  and  this  is  the  only  sense  in  which 
gravity  can  be  said  to  be  converted  into  heat.  In  no  case 
is  the  force  which  produces  the  motion  annihilated  or 
changed  into  anything  else.  The  mutual  attraction  of 
the  earth  and  weight  exists  when  they  are  in  contact,  as 
when  they  were  separate  ;  but  the  ability  of  that  attrac- 
tion to  employ  itself  in  the  production  of  motion  does  not 
exist. 

The  transformation,  in  this  case,  is  easily  followed  by 
the  mind's  eye.  First,  the  weight  as  a  whole  is  set  in 
motion  by  the  attraction  of  gravity.  This  motion  of  the 
mass  is  arrested  by  collision  with  the  earth,  being  broken 
up  into  molecular  tremors,  to  which  we  give  the  name  of 
heat. 

And  when  we  reverse  the  process,  and  employ  those 
tremors  of  heat  to  raise  a  weight,  which  is  done  through 
the  intermediation  of  an  elastic  fluid  in  the  steam-engine, 
a  certain  definite  portion  of  the  molecular  motion  is  con- 
sumed. In  this  sense,  and  in  this  sense  only,  can  the  heat 
be  said  to  be  converted  into  gravity ;  or,  more  correctly, 
into  potential  energy  of  gravity.  Here  the  destruction 
of  the  heat  has  created  no  new  attraction ;  but  the  old 
attraction  has  conferred  upon  it  a  power  of  exerting  a 
certain  definite  pull,  between  the  starting-point  of  the 
falling  weight  and  the  earth. 

When,  therefore,  writers  on  the  conservation  of  energy 
speak  of  tensions  being  '  consumed '  and  '  generated,'  they 
do  not  mean  thereby  that  old  attractions  have  been  anni- 
hilated, and  new  ones  brought  into  existence,  but  that-, 
in  the  one  case,  the  power  of  the  attraction  to  produce 
motion  has  been  diminished  by  the  shortening  of  the  dis- 
tance between  the  attracting  bodies,  while,  in  the  other 
case,  the  power  of  producing  motion  has  been  augmented 


26  FRAGMENTS    OF   SCIENCE. 

by  the  increase  of  the  distance.     These  remarks  apply  to 
all  bodies,  whether  they  be  sensible  masses  or  molecules. 

Of  the  inner  quality  that  enables  matter  to  attract 
matter  we  know  nothing ;  and  the  law  of  conservation 
makes  no  statement  regarding  that  quality.  It  takes  the 
facts  of  attraction  as  they  stand,  and  affirms  only  the 
constancy  of  working-power.  That  power  may  exist  in 
the  form  of  MOTION  ;  or  it  may  exist  in  the  form  of  FORCE, 
with  distance  to  act  through.  The  former  is  dynamic 
energy,  the  latter  is  potential  energy,  the  constancy  of  the 
sum  of  both  being  affirmed  by  the  law  of  conservation. 
The  convertibility  of  natural  forces  consists  solely  in  trans- 
formations of  dynamic  into  potential,  and  of  potential  into 
dynamic  energy.  In  no  other  sense  has  the  convertibility 
of  force  any  scientific  meaning. 


From  the  writings  and  conversation  of  distinguished 
men  I  learned,  that  the  notion  of  gravity  being  an  out- 
standing force,  entirely  inconvertible,  was  prevalent  among 
them.  Hence  the  origin  of  the  foregoing  exposition. 
Grave  errors  have,  indeed,  been  entertained,  as  to  what  is 
really  intended  to  be  conserved  by  the  doctrine  of  con- 
servation. November  1875. 


II. 

RADIATION 

1865. 

1.   Visible  and  Invisible,  Radiation. 

T)ETWEEN  the  mind  of  man  and  the  outer  world  are 
\J  interposed  the  nerves  of  the  human  body,  which 
translate,  or  enable  the  mind  to  translate,  the  impressions 
of  that  world  into  facts  of  consciousness  and  thought. 

Different  nerves  are  suited  to  the  perception  of 
different  impressions.  We  do  not  see  with  the  ear,  nor 
hear  with  the  eye,  nor  are  we  rendered  sensible  of  sound 
by  the  nerves  of  the  tongue.  Out  of  the  general  assemblage 
of  physical  actions,  each  nerve,  or  group  of  nerves,  selects 
and  responds  to  those  for  the  perception  of  which  it  is 
specially  organised. 

The  optic  nerve  passes  from  the  brain  to  the  back  of 
the  eyeball  and  there  spreads  out,  to  form  the  retina,  a 
web  of  nerve  filaments,  on  which  the  images  of  external 
objects  are  projected  by  the  optical  portion  of  the  eye. 
This  nerve  is  limited  to  the  apprehension  of  the  phe- 
nomena of  radiation,  and,  notwithstanding  its  marvellous 
sensibility  to  certain  impressions  of  this  class,  it  is 
singularly  obtuse  to  other  impressions. 

.Nor  does  the  optic  nerve  embrace  the  entire  range 

even  of  radiation.     Some  rays,  when  they  reach   it,  are 

incompetent  to  evoke  its  power,  while  others  never  reach 

it  at  all,  being  absorbed  by  the  humours  of  the  eye.     To 

4 


28  FRAGMENTS   OF   SCIENCE. 

all  rays  which,  whether  they  reach  the  retina  or  not,  fail 
to  excite  vision,  we  give  the  name  of  invisible  or  obscure 
rays.  All  non-luminous  bodies  emit  such  rays.  There 
is  no  body  in  nature  absolutely  cold,  and  every  body  not 
absolutely  cold  emits  rays  of  heat.  But  to  render  radiant 
heat  fit  to  affect  the  optic  nerve  a  certain  temperature  is 
necessary.  A  cool  poker  thrust  into  a  fire  remains  dark 
for  a  time,  but  when  its  temperature  has  become  equal 
to  that  of  the  surrounding  coals,  it  glows  like  them.  In 
like  manner,  if  a  current  of  electricity,  of  gradually  in- 
creasing strength,  be  sent  through  a  wire  of  the  refractory 
metal  platinum,  the  wire  first  becomes  sensibly  warm  to 
«he  touch  ;  for  a  time  its  heat  augments,  still  however 
remaining  obscure ;  at  length  we  can  no  longer  touch  the 
metal  with  impunity ;  and  at  a  certain  definite  temper- 
ature it  emits  a  feeble  red  light.  As  the  current  aug- 
ments in  power  the  light  augments  in  brilliancy,  until 
finally  the  wire  appears  of  a  dazzling  white.  The  light 
which  it  now  emits  is  similar  to  that  of  the  sun. 

By  means  of  a  prism  Sir  Isaac  Newton  unravelled  the 
texture  of  solar  light,  and  by  the  same  simple  instrument 
we  can  investigate  the  luminous  changes  of  our  platinum 
wire.  In  passing  through  the  prism  all  its  rays  (and 
they  are  infinite  in  variety)  are  bent  or  refracted  from 
their  straight  course ;  and,  as  different  rays  are  differently 
refracted  by  the  prism,  we  are  by  it  enabled  to  separate 
one  class  of  rays  from  another.  By  such  prismatic  analy- 
sis Dr.  Draper  has  shown,  that  when  the  platinum  wire 
first  begins  to  glow,  the  light  emitted  is  sensibly  red.  As 
the  glow  augments  the  red  becomes  more  brilliant,  but  at 
the  same  time  orange  rays  are  added  to  the  emission. 
Augmenting  the  temperature  still  further,  yellow  raya 
appear  beside  the  orange  ;  after  the  yellow,  green  rays  are 
emitted ;  and  after  the  green  come,  in  succession,  blue, 
indigo,  and  violet  rays.  To  display  all  these  colours  at 


RADIATION.  29 

the  same  time  the  platinum  wire  must  be  white-hot:  the 
impression  of  whiteness  being  in  fact  produced  by  the 
simultaneous  action  of  all  these  colours  on  the  optic  nerve. 

In  the  experiment  just  described  we  began  with  a 
platinum  wire  at  an  ordinary  temperature,  and  gradually 
raised  it  to  a  white  heat.  At  the  beginning,  and  even 
before  the  electric  current  had  acted  at  all  upon  the  wire, 
it  emitted  invisible  rays.  For  some  time  after  the  action 
of  the  current  had  commenced,  and  even  for  a  time  after 
the  wire  had  become  intolerable  to  the  touch,  its  radia- 
tion was  still  invisible.  The  question  now  arises,  What 
becomes  of  these  invisible  rays  when  the  visible  ones 
make  their  appearance  ?  It  will  be  proved  in  the  sequel 
that  they  maintain  themselves  in  the  radiation ;  that  a 
ray  once  emitted  continues  to  be  emitted  when  the  tem- 
perature is  increased,  and  hence  the  emission  from  our 
platinum  wire,  even  when  it  has  attained  its  maximum 
brilliancy,  consists  of  a  mixture  of  visible  and  invisible 
rays.  If,  instead  of  the  platinum  wire,  the  earth  itself 
were  raised  to  incandescence,  the  obscure  radiation  which 
it  now  emits  would  continue  to  be  emitted.  To  reach 
incandescence  the  planet  would  have  to  pass  through  all 
the  stages  of  non-luminous  radiation,  and  the  final  emis- 
sion would  embrace  the  rays  of  all  these  stages.  There 
can  hardly  be  a  doubt  that  from  the  sun  itself,  rays  pro- 
ceed similar  in  kind  to  those  which  the  dark  earth  pours 
nightly  into  space.  In  fact,  the  various  kinds  of  obscure 
rays  emitted  by  all  the  planets  of  our  system  are  included 
in  the  present  radiation  of  the  sun. 

The  great  pioneer  in  this  domain  of  science  was  Sir 
William  Herschel.  Causing  a  beam  of  solar  light  to  pass 
through  a  prism,  he  resolved  it  into  its  coloured  consti- 
tuents; he  formed  what  is  technically  called  the  solar 
spectrum.  Exposing  thermometers  to  the  successive 
colours  he  determined  their  heating  power,  and  found  it 


30  FRAGMENTS   OF   SCIENCE. 

to  augment  from  the  violet  or  most  refracted  end,  to  the 
red  or  least  refracted  end  of  the  spectrum.  But  he  did 
not  stop  here.  Pushing  his  thermometers  into  the  dark 
space  beyond  the  red  he  found  that,  though  the  light 
had  disappeared,  the  radiant  heat  falling  on  the  instru- 
ments was  more  intense  than  that  at  any  visible  part  of 
the  spectrum.  In  fact,  Sir  William  Herschel  showed, 
and  his  results  have  been  verified  by  various  philosophers 
since  his  time,  that,  besides  its  luminous  rays,  the  sun 
pours  forth  a  multitude  of  other  rays,  more  powerfully 
calorific  than  the  luminous  ones,  but  entirely  unsuited  to 
the  purposes  of  vision. 

At  the  less  refrangible  end  of  the  solar  spectrum,  then, 
the  range  of  the  sun's  radiation  is  not  limited  by  that  of 
the  eye.  The  same  statement  applies  to  the  more  refrang- 
ible end.  Eitter  discovered  the  extension  of  the  spec- 
trum into  the  invisible  region  beyond  the  violet ;  and,  in 
recent  times,  this  ultra-violet  emission  has  had  peculiar 
interest  conferred  upon  it  by  the  admirable  researches  of 
Professor  Stokes.  The  complete  spectrum  of  the  sun 
consists,  therefore,  of  three  distinct  parts  : — first,  of  ultra- 
red  rays  of  high  heating  power,  but  unsuited  to  the  pur- 
poses of  vision  ;  secondly,  of  luminous  rays  which  display 
the  succession  of  colours,  red,  orange,  yellow,  green,  blue, 
indigo,  violet ;  thirdly,  of  ultra-violet  rays  which,  like  the 
ultra-red  ones,  are  incompetent  to  excite  vision,  but  which, 
unlike  the  ultra-red  rays,  possess  a  very  feeble  heating 
power.  In  consequence,  however,  of  their  chemical  energy 
these  ultra-violet  rays  aie  of  the  utmost  importance  to 
the  organic  world. 


KADIATIOX.  31 


2.  Origin  and  Character  of  Radiation.     The  Aether. 

When  we  see  a  platinum  wire  raised  gradually  to  a 
white  heat,  and  emitting  in  succession  all  the  colou  s  of  the 
spectrum,  we  are  simply  conscious  of  a  series  of  changes 
in  the  condition  of  ouv  own  eyes.  We  do  not  see  the 
actions  in  which  these  successive  colours  originate,  but  the 
mind  irresistibly  infers  that  the  appearance  of  the  colours 
corresponds  to  certain  contemporaneous  changes  in  the 
wire.  What  is  the  nature  of  these  changes  ?  In  virtue 
of  what  condition  does  the  wire  radiate  at  all  ?  We  must 
now  look  from  the  wire,  as  a  whole,  to  its  constituent  atoms. 
Could  we  see  those  atoms,  even  before  the  electric  current 
has  begun  to  act  upon  them,  we  should  find  them  in  a 
state  of  vibration.  In  this  vibration,  indeed,  consists  such 
warmth  as  the  wire  then  possesses.  Locke  enunciated  this 
idea  with  great  precision,  and  it  has  been  placed  beyond  the 
pale  of  doubt  by  the  excellent  quantitative  researches  of 
Mr.  Joule.  '  Heat,'  says  Locke, '  is  a  very  brisk  agitation 
of  the  insensible  parts  of  the  object,  which  produce  in  us 
that  sensation  from  which  we  denominate  the  object  hot : 
so  what  in  our  sensations  is  heat  in  the  object  is  nothing 
but  motion.'  When  the  electric  current,  still  feeble,  begins 
to  pass  through  the  wire,  its  first  act  is  to  intensify  the 
vibrations  already  existing,  by  causing  the  atoms  to  swing 
through  wider  ranges.  Technically  speaking,  the  ampli- 
tudes of  the  oscillations  are  increased.  The  current  does 
this,  however,  without  altering  the  periods  of  the  old 
vibrations,  or  the  times  in  which  they  were  executed.  But 
besides  intensifying  the  old  vibrations  the  current  gene- 
rates new  and  more  rapid  ones,  and  when  a  certain  de- 
finite rapidity  has  been  attained,  the  wire  begins  to  glow. 
The  colour  first  exhibited  is  red,  which  corresponds  to  the 
lowest  rate  of  vibration  of  which  the  eye  is  able  to  take 


32  FRAGMENTS   OF   SCIEXCE. 

cognisance.  By  augmenting  the  strength  of  the  electric 
current  more  rapid  vibrations  are  introduced,  and  orange 
rays  appear.  A  quicker  rate  of  vibration  produces  yellow, 
a  still  quicker  green;  and  by  further  augmenting  the 
rapidity,  we  pass  through  blue,  indigo,  and  violet,  to  the 
extreme  ultra-violet  rays. 

Such  are  the  changes  which  science  recognises  in  the 
wire  itself,  as  concurrent  with  the  visual  changes  taking 
place  in  the  eye.  But  what  connects  the  wire  with  this 
organ  ?  By  what  means  does  it  send  such  intelligence  of 
its  varying  condition  to  the  optic  nerve  ?  Heat  being,  as 
defined  by  Locke,  c  a  very  brisk  agitation  of  the  insen- 
sible parts  of  an  object,'  it  is  readily  conceivable  that  on 
touching  a  heated  body  the  agitation  may  communicate 
itself  to  the  adjacent  nerves,  and  announce  itself  to  them 
as  light  or  heat.  But  the  optic  nerve  does  not  touch  the 
hot  platinum,  and  hence  the  pertinence  of  the  question, 
By  what  agency  are  the  vibrations  of  the  wire  transmitted 
to  the  eye  ? 

The  answer  to  this  question  involves  perhaps  the  most 
important  physical  conception  that  the  mind  of  man  has 
yet  achieved :  the  conception  of  a  medium  filling  space 
and  fitted  mechanically  for  the  transmission  of  the  vibra- 
tions of  light  and  heat,  as  air  is  fitted  for  the  transmission 
of  sound.  This  medium  is  called  the  luminiferous  aether. 
Every  vibration  of  every  atom  of  our  platinum  wire  raises 
in  this  aether  a  wave,  which  speeds  through  it  at  the  rate 
of  186,000  miles  a  second.  The  aether  suffers  no  rupture 
of  continuity  at  the  surface  of  the  eye,  the  inter-molecular 
spaces  of  the  various  humours  are  filled  with  it ;  hence 
the  waves  generated  by  the  glowing  platinum  can  cross 
these  humours  and  impinge  on  the  optic  nerve  at  the 
back  of  the  eye.  Thus  the  sensation  of  light  reduces  itself 
to  the  communication  of  motion.  Up  to  this  point  we 
deal  with  pure  mechanics  ;  but  the  subsequent  translation 


RADIATION.  33 

of  the  shock  of  the  aethereal  waves  into  consciousness 
eludes  the  analysis  of  science.  As  an  oar  dipping  into 
the  Cam  generates  systems  of  waves,  which,  speeding  from 
the  centre  of  disturbance,  finally  stir  the  sedges  on  the 
river's  bank,  so  do  the  vibrating  atoms  generate  in  the 
surrounding  aether  undulations,  which  finally  stir  the  fila- 
ments of  the  retina.  The  motion  thus  imparted  is  trans- 
mitted with  measurable,  and  not  very  great  velocity  to 
the  brain,  where,  by  a  process  which  science  does  not  even 
tend  to  unravel,  the  tremor  of  the  nervous  matter  is  con- 
verted into  the  conscious  impression  of  light. 

Darkness  might  then  be  defined  as  aether  at  rest ;  light 
as  aether  in  motion.  But  in  reality  the  aether  is  never  at 
rest,  for  in  the  absence  of  light- waves  we  have  heat-waves 
always  speeding  through  it.  In  the  spaces  of  the  universe 
both  classes  of  undulations  incessantly  commingle.  Here 
the  waves  issuing  from  uncounted  centres  cross,  coincide, 
oppose,  and  pass  through  each  other,  without  confusion 
or  ultimate  extinction.  The  waves  from  the  zenith  do  not 
jostle  out  of  existence  those  from  the  horizon,  and  every 
star  is  seen  across  the  entanglement  of  wave-motions 
produced  by  all  other  stars.  It  is  the  ceaseless  thrill 
caused  by  those  distant  orbs  collectively  in  the  aether, 
that  constitutes  what  we  call  the  temperature  of  space. 
As  the  air  of  a  room  accommodates  itself  to  the  require- 
ments of  an  orchestra,  transmitting  each  vibration  of  every 
pipe  and  string,  so  does  the  inter-stellar  aether  accommo- 
date itself  to  the  requirements  of  light  and  heat.  Its 
waves  mingle  in  space  without  disorder,  each  being 

u  dowed  with  an  individuality  as  indestructible  as  if  it 
alone  had  disturbed  the  universal  repose. 

All  vagueness  with  regard  to  the  use  of  the    terms 

radiation  and  absorption  will  now  disappear.     Eadiation 

is  the  communication  of  vibratory  motion  to  the  aether  ; 

and  when  a  body  is  said  to  be  chilled  by  radiation,  as  for 


34  FRAGMENTS   OP   SCIENCE. 

example  the  grass  of  a  meadow  on  a  starlight  night,  the 
meaning  is,  that  the  molecules  of  the  grass  have  lost  a 
portion  of  their  motion,  by  imparting  it  to  the  medium 
in  which  they  vibrate.  On  the  other  hand,  the  waves  of 
aether  may  so  strike  against  the  molecules  of  a  body 
exposed  to  their  action  as  to  yield  up  their  motion  to 
the  latter ;  and  in  this  transfer  of  the  motion  from  the 
aether  to  the  molecules  consists  the  absorption  of  radiant 
heat.  All  the  phenomena  of  heat  are  in  this  way  re- 
ducible to  interchanges  of  motion ;  and  it  is  purely  as 
the  recipients  or  the  donors  of  this  motion,  that  we  our- 
selves become  conscious  of  the  action  of  heat  and  cold. 


3.  The  Atomic  Theory  in  reference  to  the  Aether. 

The  word  '  atoms'  has  been  more  than  once  employed 
in  this  discourse.  Chemists  have  taught  us  that  all  matter 
is  reducible  to  certain  elementary  forms  to  which  they 
give  this  name.  These  atoms  are  endowed  with  powers 
of  mutual  attraction,  and  under  suitable  circumstances 
they  coalesce  to  form  compounds.  Thus  oxygen  and 
hydrogen  are  elements  when  separate,  or  merely  mixed, 
but  they  may  be  made  to  combine  so  as  to  form  molecules, 
each  consisting  of  two  atoms  of  hydrogen  and  one  of 
oxygen.  In  this  condition  they  constitute  water.  So 
also  chlorine  and  sodium  are  elements,  the  former  a  pun- 
gent gas,  the  latter  a  soft  metal ;  and  they  unite  together 
to  form  chloride  of  sodium  or  common  salt.  In  the  same 
way  the  element  nitrogen  combines  with  hydrogen,  in  the 
proportion  of  one  atom  of  the  former  to  three  of  the  latter, 
to  form  ammonia,  or  spirit  of  hartshorn.  Picturing  in 
imagination  the  atoms  of  elementary  bodies  as  little  spheres, 
the  molecules  of  compound  bodies  must  be  pictured  as 
groups  of  such  spheres.  This  is  the  atomic  theory  as 


KADIATIOff.  35 

Dalton  conceived  it.  Now  if  this  theory  have  any  founda- 
tion in  fact,  and  if  the  theory  of  an  aether  pervading 
space,  and  constituting  the  vehicle  of  atomic  motion,  be 
founded  in  fact,  we  may  assuredly  expect  the  vibrations  of 
elementary  bodies  to  be  profoundly  modified  by  the  act  of 
combination.  It  is  on  the  face  of  it  almost  certain  that 
both  as  regards  radiation  and  absorption,  that  is  to  say, 
both  as  regards  the  communication  of  motion  to  the  aether, 
and  the  acceptance  of  motion  from  it,  the  deportment  of 
the  uncombined  atoms  will  be  different  from  thdt  of  the 
combined. 


4.  Absorption  of  Radiant  Heat  by  Gases. 

We  have  now  to  submit  these  considerations  to  the  only 
test  by  which  they  can  be  tried,  namely,  that  of  experi 
ment.  An  experiment  is  well  defined  as  a  question  put 
to  Nature  ;  but,  to  avoid  the  risk  of  asking  amiss,  we  ought 
to  purify  the  question  from  all  adjuncts  which  do  not 
necessarily  belong  to  it.  Matter  has  been  shown  to  be 
composed  of  elementary  constituents,  by  the  compounding 
of  which  all  its  varieties  are  produced.  But,  besides  the 
chemical  unions  which  they  form,  both  elementary  and 
compound  bodies  can  unite  in  another  and  less  intimate 
way.  By  the  attraction  of  cohesion  gases  and  vapours 
aggregate  to  liquids  and  solids,  without  any  change  of  their 
chemical  nature.  We  do  not  yet  know  how  the  transmis- 
sion of  radiant  heat  may  be  affected  by  the  entanglement 
due  to  cohesion ;  and,  as  our  object  now  is  to  examine  the 
influence  of  chemical  union  alone,  we  shall  render  our 
experiments  more  pure  by  liberating  the  atoms  and  mole- 
cules entirely  from  the  bonds  of  cohesion,  and  employing 
them  in  the  gaseous  or  vaporous  form. 

Let  us  endeavour  to  obtain  a  perfectly  clear  mental 


86  FRAGMENTS   OP   SCIENCE. 

image  of  the  problem  now  before  us.  Limiting  in  the 
first  place  our  enquiries  to  the  phenomena  of  absorption, 
we  have  to  picture  a  succession  of  waves  issuing  from  a 
radiant  source  and  passing  through  a  gas  ;  some  of  them 
striking  against  the  gaseous  molecules  and  yielding  up 
their  motion  to  the  latter ;  others  gliding  round  the  mole- 
cules, or  passing  through  the  inter-molecular  spaces  with- 
out apparent  hindrance.  The  problem  before  us  is  to 
determine  whether  such  free  molecules  have  any  power 
whatever  to  stop  the  waves  of  heat ;  and  if  so,  whether  dif- 
ferent molecules  possess  this  power  in  different  degrees. 

The  source  of  waves  chosen  for  these  experiments 
is  a  plate  of  copper,  against  the  back  of  which  a 
steady  sheet  of  flame  is  permitted  to  play.  On  emerging 
from  the  copper,  the  waves,  in  the  first  instance,  pass 
through  a  space  devoid  of  air,  and  then  enter  a  hollow 
glass  cylinder,  three  feet  long  and  three  inches  wide.  The 
two  ends  of  this  cylinder  are  stopped  by  two  plates  of  rock- 
salt,  this  being  the  only  solid  substance  which  offers  a 
scarcely  sensible  obstacle  to  the  passage  of  the  calorific 
waves.  After  passing  through  the  tube,  the  radiant  heat 
falls  upon  the  anterior  face  of  a  thermo-electric  pile,1 
which  instantly  applies  the  heat  to  the  generation  of  an 
electric  current.  This  current  conducted  round  a  mag- 
netic needle  deflects  it,  and  the  magnitude  of  the  deflection 
is  a  measure  of  the  heat  falling  upon  the  pile.  This 
famous  instrument,  and  not  an  ordinary  thermometer,  is 
.vhat  we  shall  use  in  these  enquiries,  but  we  shall  use  it 
in  a  somewhat  novel  way.  As  long  as  the  two  opposite 
faces  of  the  thermo-electric  pile  are  kept  at  the  same  tem- 
perature, no  matter  how  high  that  may  be,  there  is  no 
current  generated.  The  current  is  a  consequence  of  a 

1  In  the  Appendix  to  the  first  chapter  of  '  Heat  as  a  Mode  of  Motion- 
the  construction  of  the  thermo-electric  pile  is  fully  explained. 


RADIATION.  37 

difference  of  temperature  between  the  two  opposite  faces 
of  the  pile.  Hence,  if  after  the  anterior  face  has  received 
the  heat  from  our  radiating  source,  a  second  source,  which 
we  may  call  the  -  compensating  source,  be  permitted  to 
radiate  against  the  posterior  face,  this  latter  radiation  will 
tend  to  neutralise  the  former.  When  the  neutralisation 
is  perfect,  the  magnetic  needle  connected  with  the  pile  is 
no  longer  deflected,  but  points  to  the  zero  of  the  graduated 
circle  over  which  it  hangs. 

And  now  let  us  suppose  the  glass  tube,  through  which 
pass  the  waves  from  the  heated  plate  of  copper,  to  be  ex- 
hausted by  an  air-pump,  the  two  sources  of  heat  acting  at 
the  same  time  on  the  two  opposite  faces  of  the  pile. 
Perfectly  equal  quantities  of  heat  being  imparted  to  the 
two  faces,  the  needle  points  to  zero.  Let  any  gas  be  now 
permitted  to  enter  the  exhausted  tube ;  if  the  molecules 
possess  any  power  of  intercepting  the  calorific  waves,  the 
equilibrium  previously  existing  will  be  destroyed,  the 
compensating  source  will  triumph,  and  a  deflection  of  the 
magnetic  needle  will  be  the  immediate  consequence.  From 
the  deflections  thus  produced  by  different  gases,  we  can 
readily  deduce  the  relative  amounts  of  wave-motion  which 
their  molecules  intercept. 

In  this  way  the  substances  mentioned  in  the  following 
table  were  examined,  a  small  portion  only  of  each  being 
admitted  into  the  glass  tube.  The  quantity  admitted  was 
just  sufficient  to  depress  a  column  of  mercury  associated 
with  the  tube  one  inch :  in  other  words,  the  gases  were 
examined  at  a  pressure  of  one-thirtieth  of  an  atmosphere. 
The  numbers  in  the  table  express  the  relative  amounts 
of  wave-motion  absorbed  by  the  respective  gases,  the 
quantity  intercepted  by  atmospheric  air  being  taken  a* 
unity. 


88  FRAGMENTS   OF    SCIENCE. 

Radiation  through  Gases. 

Name  of  gas  Relatlre 

absorption 

Air 1 

Oxygen       1 

Nitrogen 1 

Hydrogen 1 

Carbonic  oxide 750 

Carbonic  acid 972 

Hydrochloric  acid         ....  1,005 

Nitric  oxide 1,590 

Nitrous  oxide 1,860 

Sulphido  of  hydrogen  .         .         .         .2,100 

Ammonia 5,460 

Olefiantgas 6,030 

Sulphurous  acid 6,480 

Every  gas  in  this  table  is  perfectly  transparent  to  light, 
that  is  to  say,  all  waves  within  the  limits  of  the  visible 
spectrum  pass  through  it  without  obstruction  ;  but  for  the 
waves  of  slower  period,  emanating  from  our  heated  plate 
of  copper,  enormous  differences  of  absorptive  power  are 
manifested.  These  differences  illustrate  in  the  most  un- 
expected manner  the  influence  of  chemical  combination. 
Thus  the  elementary  gases,  oxygen,  hydrogen,  and  nitro- 
gen, and  the  mixture  atmospheric  air,  prove  to  be  practical 
vacua  to  the  rays  of  heat ;  for  every  ray,  or,  more  strictly 
speaking,  for  every  unit  of  wave-motion,  which  any  one 
of  them  is  competent  to  intercept,  perfectly  transparent 
ammonia  intercepts  5,460  units,  olefiant  gas  6,030  units, 
while  sulphurous  acid  gas  absorbs  6,480  units.  What 
becomes  of  the  wave-motion  thus  intercepted?  It  is 
applied  to  the  heating  of  the  absorbing  gas.  Through 
air,  oxygen,  hydrogen,  and  nitrogen,  on  the  contrary,  the 
waves  of  aether  pass  without  absorption,  and  these  gases 
are  not  sensibly  changed  in  temperature  by  the  most 
powerful  calorific  rays.  The  position  of  nitrous  oxide  in 
the  foregoing  table  is  worthy  of  particular  notice.  In  this 
gas  we  have  the  same  atoms  in  a  state  of  chemical  union. 


RADIATION.  39 

that  exist  uncombined  in  the  atmosphere ;  but  the  absorp- 
tion of  the  compound  is  1,800  times  that  of  air. 


5.  Formation  of  Invisible  Foci. 

This  extraordinary  deportment  of  the  elementary  gases 
naturally  directed  attention  to  elementary  bodies  in 
other  states  of  aggregation.  Some  of  Melloni's  results 
now  attained  a  new  significance ;  for  this  celebrated  ex- 
perimenter had  found  crystals  of  the  element  sulphur  to 
be  highly  pervious  to  radiant  heat ;  he  had  also  proved 
that  lamp-black,  and  black  glass,  (which  owes  its  blackness 
to  the  element  carbon)  were  to  a  considerable  extent 
transparent  to  calorific  rays  of  low  refrangibility.  These 
facts,  harmonising  so  strikingly  with  the  deportment  of 
the  simple  gases,  suggested  further  enquiry.  Sulphur  dis- 
solved in  bisulphide  of  carbon  was  found  almost  perfectly 
transparent.  The  dense  and  deeply-coloured  element 
bromine  was  examined,  and  found  competent  to  cut  off 
the  light  of  our  most  brilliant  flames,  while  it  transmitted 
the  invisible  calorific  rays  with  extreme  freedom.  Iodine, 
the  companion  element  of  bromine,  was  next  thought  of, 
but  it  was  found  impracticable  to  examine  the  substance 
in  its  usual  solid  condition.  It  however  dissolves  freely 
in  bisulphide  of  carbon.  There  is  no  chemical  union 
between  the  liquid  and  the  iodine ;  it  is  simply  a  case  of 
solution,  in  which  the  uncombined  atoms  of  the  element 
can  act  upon  the  radiant  heat.  When  permitted  to  do  so, 
it  was  found  that  a  layer  of  dissolved  iodine,  sufficiently 
opaque  to  cut  off  the  light  of  the  midday  sun,  was  almost 
absolutely  transparent  to  the  invisible  calorific  rays. 

By  prismatic  analysis  Sir  William  Herschel  separated 
the  luminous  from  the  non-luminous  rays  of  the  sun,  and 
he  also  sought  to  render  the  obscure  rays  visible  by  con- 


40  FRAGMENTS   OF   SCIENCE. 

centration.  Intercepting  the  luminous  portion  of  his 
spectrum  he  brought,  by  a  converging  lens,  the  ultra-red 
rays  to  a  focus,  but  by  this  condensation  he  obtained  no 
light.  The  solution  of  iodine  offers  a  means  of  filtering 
the  solar  beam,  or,  failing  it,  the  beam  of  the  electric 
lamp,  which  renders  attainable  far  more  powerful  foci  of 
invisible  rays  than  could  possibly  be  obtained  by  the 
method  of  Sir  William  Herschel.  For  to  form  his  spec- 
trum he  was  obliged  to  operate  upon  solar  light  which 
had  passed  through  a  narrow  slit  or  through  a  small 
aperture,  the  amount  of  the  obscure  heat  being  limited 
by  this  circumstance.  But  with  our  opaque  solution 
we  may  employ  the  entire  surface  of  the  largest  lens, 
and  having  thus  converged  the  rays,  luminous  and  non- 
luminous,  we  can  intercept  the  former  by  the  iodine, 
and  do  what  we  please  with  the  latter.  Experiments  of 
this  character,  not  only  with  the  iodine  solution,  but  also 
Avith  black  glass  and  layers  of  lamp-black,  were  publicly 
performed  at  the  Eoyal  Institution  in  the  early  part  of 
1862,  and  the  effects  at  the  foci  of  invisible  rays,  then  ob- 
tained, were  such  as  had  never  been  witnessed  previously. 
In  the  experiments  here  referred  to,  glass  lenses  were 
employed  to  concentrate  the  rays.  But  glass,  though 
highly  transparent  to  the  luminous,  is  in  a  high  degree 
opaque  to  the  invisible,  heat-rays  of  the  electric  lamp,  and 
hence  a  large  portion  of  those  rays  was  intercepted  by  the 
j  lass.  The  obvious  remedy  here  is  to  employ  rock-salt 
lenses  instead  of  glass  ones,  or  to  abandon  the  use  of 
lenses  wholly,  and  to  concentrate  the  rays  by  a  metallic 
mirror.  Both  of  these  improvements  have  been  intro- 
duced, and,  as  anticipated,  the  invisible  foci  have  been 
thereby  rendered  more  intense.  The  mode  of  operating 
remains  however  the  same,  in  principle,  as  that  made 
known  in  1862.  It  was  then  found  that  an  instant's  ex- 
posure of  the  face  of  the  thermo-electric  pile  to  the  focus 


RADIATION.  41 

of  invisible  rays,  dashed  the  needles  of  a  coarse  galva- 
nometer violently  aside.  It  is  now  found  that,  on  substi- 
tuting for  the  face  of  the  thermo-electric  pile  a  com- 
bustible body,  the  invisible  rays  are  competent  to  set  that 
body  on  fire. 


6.   Visible  and  Invisible  Rays  of  the  Electric  Light. 

We  have  next  to  examine  what  proportion  the  non- 
luminous  rays  of  the  electric  light  bear  to  the  luminous 
ones.  This  the  opaque  solution  of  iodine  enables  us  to  do 
with  an  extremely  close  approximation  to  the  truth.  The 
pure  bisulphide  of  carbon,  which  is  the  solvent  of  the 
iodine,  is  perfectly  transparent  to  the  luminous,  and 
almost  perfectly  transparent  to  the  dark,  rays  of  the 
electric  lamp.  Through  the  transparent  bisulphide  the 
total  radiation  of  the  lamp  may  be  considered  to  pass, 
while  through  the  solution  of  iodine  only  the  dark  rays 
are  transmitted.  Determining,  then,  by  means  of  a 
thermo-electric  pile,  the  total  radiation,  and  deducting 
from  it  the  purely  obscure,  we  obtain  the  amount  of  the 
purely  luminous  emission.  Experiments,  performed  in 
this  way,  prove  that  if  all  the  visible  rays  of  the  electric 
light  were  converged  to  a  focus  of  dazzling  brilliancy,  its 
heat  would  only  be  one-eighth  of  that  produced  at  the 
unseen  focus  of  the  invisible  rays. 

Exposing  his  thermometers  to  the  successive  colours  of 
the  solar  spectrum,  Sir  William  Herschel  determined  the 
heating  power  of  each,  and  also  that  of  the  region  beyond 
the  extreme  red.  Then  drawing  a  straight  line  to  repre- 
sent the  length  of  the  spectrum,  he  erected,  at  various 
points,  perpendiculars  to  represent  the  calorific  intensity 
existing  at  those  points.  Uniting  the  ends  of  all  his 
perpendiculars,  he  obtained  a  curve  which  showed  at  a 


12  FRAGMENTS   OF   SCIENCE. 

glance  the  manner  in  which  the  heat  was  distributed  in 
the  solar  spectrum.  Professor  Miiller  of  Freiburg,  with 
improved  instruments,  afterwards  made  similar  experi- 
ments, and  constructed  a  more  accurate  diagram  of  the 
same  kind.  We  have  now  to  examine  the  distribution  of 
heat  in  the  spectrum  of  the  electric  light ;  and  for  this 
purpose  we  shall  employ  a  particular  form  of  the  thermo- 
electric pile,  devised  by  Melloni.  Its  face  is  a  rectangle, 
which  by  means  of  movable  side-pieces  can  be  rendered 
as  narrow  as  desired.  We  can,  for  example,  have  the 
face  of  the  pile  the  tenth,  the  hundredth,  or  even  the 
thousandth  of  an  inch  in  breadth.  By  means  of  an  end- 
less screw,  this  linear  thermo-electric  pile  may  be  moved 
through  the  entire  spectrum,  from  the  violet  to  the  red, 
the  amount  of  heat  falling  upon  the  pile  at  every  point 
of  its  march,  being  declared  by  a  magnetic  needle  asso- 
ciated with  the  pile. 

When  this  instrument  is  brought  up  to  the  violet  end 
of  the  spectrum  of  the  electric  light,  the  heat  is  found  to 
be  insensible.  As  the  pile  gradually  moves  from  the 
violet  end  towards  the  red,  heat  soon  manifests  itself, 
augmenting  as  we  approach  the  red.  Of  all  the  colours 
of  the  visible  spectrum  the  red  possesses  the  highest 
heating  power.  On  pushing  the  pile  into  the  dark  region 
beyond  the  red,  the  heat,  instead  of  vanishing,  rises  sud- 
denly and  enormously  in  intensity,  until  sit  some  distance 
beyond  the  red  it  attains  a  maximum.  Moving  the  pile 
still  forward,  the  thermal  power  falls,  somewhat  more 
rapidly  than  it  rose.  It  then  gradually  shades  away,  but, 
for  a  distance  beyond  the  red  greater  than  the  length  of 
the  whole  visible  spectrum,  signs  of  heat  may  be  detected. 

Drawing  a  datum  line,  and  erecting  along  it  per- 
pendiculars, proportional  in  length  to  the  thermal  in- 
tensity at  the  respective  points,  we  obtain  the  extra- 
ordinary curve,  shown  on  the  adjacent  page,  which  ex- 


RADIATION 


43 


*4  FRAGMENTS   OF  SCIENCE. 

hibits  the  distribution  of  heat  in  the  spectrum  of  the 
electric  light.  In  the  region  of  dark  rays,  beyond  the 
red,  the  curve  shoots  up  to  B,  in  a  steep  and  massive 
peak — a  kind  of  Matterhorn  of  heat,  which  dwarfs  the 
portion  of  the  diagram  ODE,  representing  the  luminous 
radiation.  Indeed,  the  idea  forced  upon  the  mind  by 
this  diagram  is  that  the  light  rays  are  a  mere  insigni- 
ficant appendage  to  the  heat-rays  represented  by  the 
area  A  B  c  D,  thrown  in  as  it  were  by  nature  for  the  pur- 
poses of  vision. 

The  diagram  drawn  by  Professor  Miiller  to  represent 
the  distribution  of  heat  in  the  solar  spectrum  is  not  by 
any  means  so  striking  as  that  just  described,  and  the 
reason,  doubtless,  is  that  prior  to  reaching  the  earth  the 
solar  rays  have  to  traverse  our  atmosphere.  By  the 
aqueous  vapour  there  diffused,  the  summit  of  the  peak 
representing  the  sun's  invisible  radiation  is  cut  off.  A 
similar  lowering  of  the  mountain  of  invisible  heat  is  ob- 
served when  the  rays  from  the  electric  light  are  permitted 
to  pass  through  a  film  of  water,  which  acts  upon  them  as 
the  atmospheric  vapour  acts  upon  the  rays  of  the  sun. 


7.  Combustion  by  Invisible  Rays. 

The  sun's  invisible  rays  far  transcend  the  visible  ones 
in  heating  power,  so  that  if  the  alleged  performances  of 
Archimedes  during  the  siege  of  Syracuse  had  any  founda- 
tion in  fact,  the  dark  solar  rays  would  have  been  the  phi- 
losopher's chief  agents  of  combustion.  On  a  small  scale 
we  can  readily  produce,  with  the  purely  invisible  rays  of 
the  electric  light,  all  that  Archimedes  is  said  to  have  per- 
formed with  the  sun's  total  radiation.  Placing  behind 
the  electric  light  a  small  concave  mirror,  the  rays  are 
converged,  the  cone  of  reflected  rays  and  their  point  of 


RADIATION.  45 

convergence  being  rendered  clearly  visible  by  the  dust 
always  floating  in  the  air.  Placing  between  the  lu- 
minous focus  and  the  source  of  rays  our  solution  of 
iodine,  the  light  of  the  cone  is  entirely  cut  away ;  but  the 
intolerable  heat  experienced  when  the  hand  is  placed, 
even  for  a  moment,  at  the  dark  focus,  shows  that  the 
calorific  rays  pass  unimpeded  through  the  opaque  solution. 
Almost  anything  that  ordinary  fire  can  effect  may  be 
accomplished  at  the  focus  of  invisible  rays  ;  the  air  at  the 
focus  remaining  at  the  same  time  perfectly  cold,  on  ac- 
count of  its  transparency  to  the  heat-rays.  An  air  ther- 
mometer, with  a  hollow  rock-salt  bulb,  would  be  unaffected 
by  the  heat  of  the  focus :  there  would  be  no  expansion, 
and  in  the  open  air  there  is  no  convection.  The  aether  at 
the  focus,  and  not  the  air,  is  the  substance  in  which  the 
heat  is  embodied.  A  block  of  wood,  placed  at  the  focus, 
absorbs  the  heat,  and  dense  volumes  of  smoke  rise  swiftly 
upwards,  showing  the  manner  in  which  the  air  itself 
would  rise,  if  the  invisible  rays  were  competent  to  heat 
it.  At  the  perfectly  dark  focus  dry  paper  is  instantly 
inflamed :  chips  of  wood  are  speedily  burnt  up  :  lead,  tin, 
and  zinc  are  fused :  and  disks  of  charred  paper  are  raised 
to  vivid  incandescence.  It  might  be  supposed  that  the 
obscure  rays  would  show  no  preference  for  black  over 
white  ;  but  they  do  show  a  preference,  and  to  obtain 
rapid  combustion,  the  body,  if  not  already  black,  ought 
to  be  blackened.  When  metals  are  to  be  burned,  it  is 
necessary  to  blacken  or  otherwise  tarnish  them,  so  as  to 
diminish  their  reflective  power.  Blackened  zinc  foil, 
when  brought  into  the  focus  of  invisible  rays,  is  instantly 
caused  to  blaze,  and  burns  with  its  peculiar  purple  flame. 
Magnesium  wire  flattened,  or  tarnished  magnesium  ribbon, 
also  bursts  into  splendid  combustion.  Pieces  of  charcoal 
suspended  in  a  receiver  full  of  oxygen  are  also  set  on 
fire :  the  dark  rays,  after  having  passed  through  the  re- 


16  FRAGMENTS   OF   SCIENCE. 

ceiver,  still  possessing  sufficient  power  to  ignite  the  char 
coal,  and  thus  initiate  the  attack  of  the  oxygen.  If, 
instead  of  being  plunged  in  oxygen,  the  charcoal  be  sus- 
pended in  vacuo,  it  immediately  glows  at  the  place  where 
the  focus  falls. 


8.  Transmutation  of  Rays :  l  Calorescence. 

Eminent  experimenters  were  long  occupied  in  demon- 
strating the  substantial  identity  of  light  and  radiant  heat, 
and  we  have  now  the  means  of  offering  a  new  and  striking 
proof  of  this  identity.  A  concave  mirror  produces,  beyond 
the  object  which  it  reflects,  an  inverted  and  magnified 
image  of  the  object ;  withdrawing,  for  example,  our  iodine 
solution,  an  intensely  luminous  inverted  image  of  the 
carbon  points  of  the  electric  light  is  formed  at  the  focus  of 
the  mirror  employed  in  the  foregoing  experiments.  When 
the  solution  is  interposed,  and  the  light  is  cut  away,  what 
becomes  of  this  image  ?  It  disappears  from  sight ;  but  an 
invisible  thermograph  remains,  and  it  is  only  the  peculiar 
constitution  of  our  eyes  that  disqualifies  us  from  seeing 
the  picture  formed  by  the  calorific  rays.  Falling  on  white 
paper,  the  image  chars  itself  out :  falling  on  black  paper, 
two  holes  are  pierced  in  it,  corresponding  to  the  images 
of  the  two  coke  points:  but  falling  on  a  thin  plate  of  carbon 
in  vacuo,  or  upon  a  thin  sheet  of  platinised  platinum,  either 
in  vacuo  or  in  air,  radiant  heat  is  converted  into  light, 
and  the  image  stamps  itself  in  vivid  incandescence  upon 
both  the  carbon  and  the  metal.  Results  similar  to  those 
obtained  with  the  electric  light  have  also  been  obtained 
witli  the  invisible  rays  of  the  lime-light  and  of  the  sun. 

Before  a  Cambridge  audience  it  is  hardly  necessary  to 
refer  to  the  excellent  researches  of  Professor  Stokes  at  the 

1  I  borrow  this  term  from  Professor  Challis,  'Philosophical  Magazine, 
ToL  xii.  p.  521. 


RADIATION.  47 

opposite  end  of  the  spectrum.  The  above  results  constitute 
a  kind  of  complement  to  his  discoveries.  Professor  Stokes 
named  the  phenomena  which  he  has  discovered  and  in- 
vestigated Fluorescence ;  for  the  new  phenomena  here 
described  I  have  proposed  the  term  Calorescence.  He, 
by  the  interposition  of  a  proper  medium,  so  lowered  the 
refrangibility  of  the  ultra-violet  rays  of  the  spectrum  as 
to  render  them  visible.  Here,  by  the  interposition  of  the 
platinum  foil,  the  refrangibility  of  the  ultra-red  rays  is 
so  exalted  as  to  render  them  visible.  Looking  through 
a  prism  at  the  incandescent  image  of  the  carbon  points, 
the  light  of  the  image  is  decomposed,  and  a  complete 
spectrum  obtained.  The  invisible  rays  of  the  electric  light, 
remoulded  by  the  atoms  of  the  platinum,  shine  thus  visibly 
forth ;  ultra-red  rays  being  converted  into  red,  orange, 
yellow,  green,  blue,  indigo,  violet,  and  ultra-violet  ones. 
Could  we,  moreover,  raise  the  original  source  of  rays  to  a 
sufficiently  high  temperature,  we  might  not  only  obtain 
from  the  dark  rays  of  such  a  source  a  single  incandescent 
image,  but  from  the  dark  rays  of  this  image  we  might  obtain 
a  second  one,  from  the  dark  rays  of  the  second  a  third, 
and  so  on — a  scries  of  complete  images  and  spectra  being 
thus  extracted  from  the  invisible  emission  of  the  primitive 
source.1 

1  On  investigating  the  calorescence  produced  by  r;iys  transmitted  through 
glasses  of  various  colours,  it  was  found  that  in  the  case  of  certain  specimens 
of  blue  glass,  the  platinum  foil  glowed  with  a  pink  or  purplish  light.  The 
eff-et  was  not  subjective,  and  considerations  of  obvious  interest  are  sug- 
gested by  it.  Different  kinds  of  black  glass  differ  notably  as  to  their  power 
of  transmitting  radiant  heat.  In  thin  plates  some  descriptions  tint  the  sun 
with  a  greenish  hue  :•  others  make  it  appear  a  glowing  red  without  any 
trace  of  green.  The  latter  are  far  more  diathermic  than  the  former.  In 
fact,  carbon  when  perfectly  dissolved,  and  incorporated  with  a  good  white 
glass,  is  highly  transparent  to  the  calorific  rays,  and  by  employing  it  as  an 
absorbent  the  phenomena  of  '  calorescence '  may  be  obtained,  though  in  a 
less  striking  form  than  with  the  iodine.  The  black  glass  chosen  for 
thermometers,  and  intended  to  absorb  completely  the  solar  heat,  may  en- 
tirely fail  in  thie  object,  if  the  glass  in  which  the  carbon  is  incorporated  be 


48  FRAGMENTS  OP   SCIENCE. 


9.  Deadness  of  the  Optic  Nerve  to  the  Calorific  Rays. 

The  layer  of  iodine  used  in  the  foregoing  experiments 
intercepted  the  rays  of  the  noonday  sun.  No  trace  of 
light  from  the  electric  lamp  was  visible  in  the  darkest  room, 
even  when  a  white  screen  was  placed  at  the  focus  of  the 
mirror  employed  to  concentrate  the  light.  It  was  thought, 
however,  that  if  the  retina  itself  were  brought  into  the 
focus  the  sensation  of  light  might  be  experienced.  The 
danger  of  this  experiment  was  twofold.  If  the  dark  rays 
were  absorbed  in  a  high  degree  by  the  humours  of  the  eye 
the  albumen  of  the  humours  might  coagulate  along  the 
line  of  the  rays.  If,  on  the  contrary,  no  such  high  absorp- 
tion took  place,  the  rays  might  reach  the  retina  with  a 
force  sufficient  to  destroy  it.  To  test  the  likelihood  of 
these  results,  experiments  were  made  on  water  and  on  a 
solution  of  alum,  and  they  showed  it  to  be  very  improbable 
that  in  the  brief  time  requisite  for  an  experiment  any 
serious  damage  could  be  done.  The  eye  was  therefore 
caused  to  approach  the  dark  focus,  no  defence,  in  the  first 
instance,  being  provided  ;  but  the  heat,  acting  upon  the 
parts  surrounding  the  pupil,  could  not  be  borne.  An 
aperture  was  therefore  pierced  in  a  plate  of  metal,  and  the 
eye,  placed  behind  the  aperture,  was  caused  to  approach 
the  point  of  convergence  of  invisible  rays.  The  focus  was 
attained,  first  by  the  pupil  and  afterwards  by  the  retina. 
Eemoving  the  eye,  but  permitting  the  plate  of  metal  to 
remain,  a  sheet  of  platinum  foil  was  placed  in  the  position 
occupied  by  the  retina  a  moment  before.  The  platinum 

colourless.  To  render  the  bulb  of  a  thermometer  a  perfect  absorbent,  the 
glass  ought  in  the  first  instance  to  be  green.  Soon  after  the  discovery  of 
fluorescence  the  late  Dr.  William  Allen  Miller  pointed  to  the  lime-Jight 
as  an  illustration  of  exalted  refrangibility.  Direct  experiments  have 
since  entirely  confirmed  the  view  expressed  at  page  210  of  his  work  on 
•Chemistry  '  published  in  1855. 


KADIATION.  49 

became  red-hot.  No  sensible  damage  was  done  to  the  eye 
by  this  experiment;  no  impression  of  light  was  produced; 
the  optic  nerve  was  not  even  conscious  of  heat. 

But  the  humours  of  the  eye  are  known  to  be  highly 
impervious  to  the  invisible  calorific  rays,  and  the  question 
therefore  arises,  '  Did  the  radiation  in  the  foregoing  expe- 
riment reach  the  retina  at  all  ? '  The  answer  is,  that  the 
rays  were  in  part  transmitted  to  the  retina,  and  in  part 
absorbed  by  the  humours.  Experiments  on  the  eye  of  an 
ox  showed  that  the  proportion  of  obscure  rays  which  reached 
the  retina  amounted  to  18  per  cent,  of  the  total  radiation  ; 
while  the  luminous  emission  from  the  electric  light  amounts 
to  no  more  than  10  per  cent,  of  the  same  total.  Were  the 
purely  luminous  rays  of  the  electric  lamp  converged  by 
our  mirror  to  a  focus,  there  can  be  no  doubt  as  to  the  fate 
of  a  retina  placed  there.  Its  ruin  would  be  inevitable  ; 
and  yet  this  would  be  accomplished  by  an  amount  of  wave- 
motion  but  little  more  than  half  of  that  which  the  retina 
bears,  without  exciting  consciousness,  at  the  focus  of  in- 
visible rays. 

This  subject  will  repay  a  moment's  further  attention. 
At  a  common  distance  of  a  foot  the  visible  radiation  of 
the  electric  light  is  800  times  the  light  of  a  candle.  At 
the  same  distance,  the  portion  of  the  radiation  of  the 
electric  light  which  reaches  the  retina,  but  fails  to  excite 
vision,  is  about  1,500  times  the  luminous  radiation  of  the 
candle.1  But  a  candle  on  a  clear  night  can  readily  be 
seen  at  a  distance  of  a  mile,  its  light  at  this  distance 
being  less  than  i0<0J,i000  of  its  light  at  the  distance  of  a 
foot.  Hence,  to  make  the  candle-light  a  mile  off  equal 
in  power  to  the  non-luminous  radiation  received  from  the 
electric  light  at  a  foot  distance,  its  intensity  would  have 

1  It  will  be  borne  in  mind  that  the  heat  which  any  ray,  luminous  or  non- 
luminous,  is  competent  to  generate  is  the  true  measure  of  the  energy  of  the 
lay. 


60  FBAGMENTS   OF   SCIENCE. 

to  be  multiplied  by  1,500x20,000,000,  or  by  thirty- 
thousand  millions.  Thus  the  thirty  thousand  millionth 
part  of  the  invisible  radiation  from  the  electric  light,  re- 
ceived by  the  retina  at  the  distance  of  a  foot,  would,  if 
slightly  changed  in  character,  be  amply  sufficient  to  pro- 
voke vision.  Nothing  could  more  forcibly  illustrate  that 
special  relationship  supposed  by  Melloni  and  others  to 
subsist  between  the  optic  nerve  and  the  oscillating  periods 
of  luminous  bodies.  The  optic  nerve  responds,  as  it  were, 
to  the  waves  with  which  it  is  in  consonance,  while  it 
refuses  to  be  excited  by  others  of  almost  infinitely  greatei 
energy,  whose  periods  of  recurrence  are  not  in  unison 
with  its  own. 

10.  Persistence  of  Rays. 

At  an  early  part  of  this  lecture  it  was  affirmed,  that 
when  a  platinum  wire  was  gradually  raised  to  a  state  of 
high  incandescence,  new  rays  were  constantly  added, 
while  the  intensity  of  the  old  ones  vas  increased.  Thus, 
in  Dr.  Draper's  experiments,  the  rise  of  temperature  that 
generated  the  orange,  yellow,  green,  and  blue  augmented 
the  intensity  of  the  red.  What  is  true  of  the  red  is  true 
of  every  other  ray  of  the  spectrum,  visible  and  invisible. 
We  cannot  indeed  see  the  augmentation  of  intensity  in 
the  region  beyond  the  red,  but  we  can  measure  it  and 
express  it  numerically.  With  this  view  the  following 
experiment  was  performed :  A  spiral  of  platinum  wire 
was  surrounded  by  a  small  glass  globe  to  protect  it  from 
currents  of  air  ;  through  an  orifice  in  the  globe  the  rays 
could  pass  from  the  spiral  and  fall  afterwards  upon  a 
thermo-electric  pile.  Placing  in  front  of  the  orifice  an 
opaque  solution  of  iodine,  the  platinum  was  gradually 
raised  from  a  low  dark  heat  to  the  fullest  incandescence, 
with  the  following  results  : — 


RADIATION.  5) 

Appearance  Eneiyy  of 

of  spiral  obscure  radiation 

Dark 1 

Dark,  but  hotter 3 

Dark,  but  still  hotter      ....         5 

Dark,  but  still  hotter      .         .         .         .10 

Feeble  red      .         .        .        .         .         .10 

Dull  red          .        .--..,.  ^.-    .         .       25 
Eed        .         .         .         .         .         .         .37 

Full  red 62 

Orange  


Bright  orange 
Yellow  . 
White    . 
Intense  white 


144 
202 
276 
440 


Thus  the  augmentation  of  the  electric  current,  which 
raises  the  wire  from  its  primitive  dark  condition  to  an 
intense  white  heat,  exalts  at  the  same  time  the  energy  of 
the  obscure  radiation,  until  at  the  end  it  is  fully  440 
times  what  it  was  at  the  beginning. 

What  has  been  here  proved  true  of  the  totality  of  the 
ultra-red  rays  is  true  for  each  of  them  singly.  Placing 
our  linear  thermo-electric  pile  in  any  part  of  the  ultra-red 
spectrum,  it  may  be  proved  that  a  ray  once  emitted  con- 
tinues to  be  emitted  with  increased  energy  as  the  tem- 
perature is  augmented.  The  platinum  spiral,  so  often 
referred  to,  being  raised  to  whiteness  by  an  electric  current, 
a  brilliant  spectrum  was  formed  from  its  light.  A  linear 
thermo-electric  pile  was  placed  in  the  region  of  obscure 
rays  beyond  the  red,  and  by  diminishing  the  current  the 
spiral  was  reduced  to  a  low  temperature.  It  was  then 
caused  to  pass  through  various  degrees  of  darkness  and 
incandescence,  with  the  following  results  : — 

Appearance  Energy  of 
of  spiral                                                              obscure  rays 

Dark 1 

Dark 6 

Faint  red 10 

Dull  red 13 

Red       .......  18 


59  FRAGMENTS   OF   SCIENCE. 

Appearance  Energy  of 

of  spiral  obscure  rays 

Full  red 27 

Orange 60 

Yellow 93 

White 122 

Here,  as  in  the  former  case,  the  dark  and  bright  ra- 
diations reached  their  maximum  together;  as  the  one 
augmented,  the  other  augmented,  until  at  last  the  energy 
of  the  obscure  rays  of  the  particular  refrangibility  here 
chosen,  became  122  times  what  it  was  at  first.  To  reach 
a  white  heat  the  wire  has  to  pass  through  all  the  stages 
of  invisible  radiation,  and  in  its  most  brilliant  condition 
it  embraces,  in  an  intensified  form,  the  rays  of  all  those 


And  thus  it  is  with  all  other  kinds  of  matter,  as  far 
as  they  have  hitherto  been  examined.  Coke,  whether 
brought  to  a  white  heat  by  the  electric  current,  or  by 
the  oxyhydrogen  jet,  pours  out  invisible  rays  with  aug- 
mented energy,  as  its  light  is  increased.  The  same  is 
true  of  lime,  bricks,  and  other  substances.  It  is  true  of 
all  metals  which  are  capable  of  being  heated  to  incan- 
descence. It  also  holds  good  for  phosphorus  burning  in 
oxygen.  Every  gush  of  dazzling  light  has  associated 
with  it  a  gush  of  invisible  radiant  heat,  which  far  tran- 
scends the  light  in  energy.  This  condition  of  things 
applies  to  all  bodies  capable  of  being  raised  to  a  white 
heat,  either  in  the  solid  or  the  molten  condition.  It 
would  doubtless  also  apply  to  the  luminous  fogs  formed 
by  the  condensation  of  incandescent  vapours.  In  such 
cases  when  the  curve  representing  the  radiant  energy  of 
the  body  is  constructed,  the  obscure  radiation  towers  up- 
wards like  a  mountain,  the  luminous  radiation  resembling 
a  mere  spur  at  its  base.  From  the  very  brightness  of  the 
light  of  some  of  the  fixed  stars  we  may  infer  the  intensity 


KADIATION.  53 

of  that  dark  radiation,  which  is  the  precursor  and  insepa- 
rable associate  of  their  luminous  rays. 

We  thus  find  the  luminous  radiation  appearing  when 
the  radiant  body  has  attained  a  certain  temperature  ;  or, 
in  other  words,  when  the  vibrating  atoms  of  the  body  have 
attained  a  certain  width  of  swing.  In  solid  and  molten 
bodies  a  certain  amplitude  cannot  be  surpassed  without 
the  introduction  of  periods  of  vibration,  which  provoke 
the  sense  of  vision.  How  are  we  to  figure  this  ?  If 
permitted  to  speculate,  we  might  ask,  are  not  these 
more  rapid  vibrations  the  progeny  of  the  slower  ?  Is  it 
not  really  the  mutual  action  of  the  atoms,  when  they 
swing  through  very  wide  spaces,  and  thus  encroach  upon 
each  other,  that  causes  them  to  tremble  in  quicker 
periods?  If  so,  whatever  be  the  agency  by  which  the 
large  swinging  space  is  obtained,  we  shall  have  light- 
giving  vibrations  associated  with  it.  It  matters  not 
whether  the  large  amplitudes  be  produced  by  the  strokes 
of  a  hammer,  or  by  the  blows  of  the  molecules  of  a  non- 
luminous  gas,  such  as  the  air  at  some  height  above  a  gas- 
flame  ;  or  by  the  shock  of  the  aether  particles  when 
transmitting  radiant  heat.  The  result  in  all  cases  will  be 
incandescence.  Thus,  the  invisible  waves  of  our  filtered 
electric  beam  may  be  regarded  as  generating  synchronous 
vibrations  among  the  atoms  of  the  platinum  on  which 
they  impinge ;  but,  once  these  vibrations  have  attained  a 
certain  amplitude,  the  mutual  jostling  of  the  atoms  pro- 
duces quicker  tremors,  and  the  light-giving  waves  follow 
us  the  necessary  product  of  the  heat-giving  ones. 

11.  Absorption  of  Radiant  Heat  by  Vapours 
and  Odours. 

We  commenced  the  demonstrations  brought  forward 
in  this  lecture  by  experiments  on  permanent  gases,  and 


54  FRAGMENTS    OF   SCIENCE. 

we  have  now  to  turn  our  attention  to  the  vapours  of 
volatile  liquids.  Here,  as  in  the  case  of  the  gases,  vast 
differences  have  been  proved  to  exist  between  various 
kinds  of  molecules,  as  regards  their  power  of  intercepting 
the  calorific  waves.  While  some  vapours  allow  the  waves 
a  comparatively  free  passage,  the  minutest  bubble  of  other 
vapours,  introduced  into  the  tube  already  employed  for 
gases,  causes  a  deflection  of  the  magnetic  needle.  Assum- 
ing the  absorption  effected  by  air,  at  a  pressure  of  one 
atmosphere,  to  be  unity,  the  following  are  the  absorptions 
effected  by  a  series  of  vapours  at  a  pressure  of  -^tk  of  an 
atmosphere : — 

Name  of  vapour  Absorption 

Bisulphide  of  carbon       ....  47 

Iodide  of  methyl 115 

Benzol 136 

Amylene 321 

Sulphuric  ether 440 

Formic  ether 548 

Acetic  ether 612 

Bisulphide  of  carbon  is  the  most  transparent  vapour  in 
this  list ;  and  acetic  ether  the  most  opaque ;  -gLth  of  an 
atmosphere  of  the  former,  however,  produces  47  times 
the  effect  of  a  whole  atmosphere  of  air,  while  -g^th  of  an 
atmosphere  of  the  latter  produces  612  times  the  effect  of 
a  whole  atmosphere  of  air.  Eeducing  dry  air  to  the  pres- 
sure of  the  acetic  ether  here  employed,  and  comparing 
them  then  together,  the  quantity  of  wave-motion  inter- 
cepted by  the  ether  would  be  many  thousand  times  that 
intercepted  by  the  air. 

Any  one  of  these  vapours  discharged  into  the  free  atmo- 
sphere, in  front  of  a  body  emitting  obscure  rays,  intercepts 
more  or  less  of  the  radiation.  A  similar  effect  is  pro- 
duced by  perfumes  diffused  in  the  air,  though  their  at- 
tenuation is  known  to  be  almost  infinite.  Carrying,  for 
example,  a  current  of  dry  air  over  bibulous  paper,  moist- 


RADIATION.  55 

ened  by  patchouli,  the  scent  taken  up  by  the  current 
absorbs  30  times  the  quantity  of  heat  intercepted  by  the 
air  which  carries  it ;  and  yet  patchouli  acts  more  feebly 
on  radiant  heat  than  any  other  perfume  yet  examined. 
Here  follow  the  results  obtained  with  various  essential 
oils,  the  odour,  in  each  case,  being  carried  by  a  current 
of  dry  air  into  the  tube  already  employed  for  gases  and 
vapours  : — 

Name  of  perfume  Absorption 

Patchouli 30 

Sandal  -wood 32 

Geranium                33 

Oil  of  cloves 34 

Otto  of  roses 37 

Bergamot 44 

Neroli 47 

Lavender        ......  60 

Lemon 65 

Portugal 67 

Thyme 68 

Rosemary 74 

Oil  of  laurel 80 

Camomile  flowers   .....  87 

Cassia 109 

Spikenard 355 

Aniseed 372 

Thus  the  absorption  by  a  tube  full  of  dry  air  being  1, 
that  of  the  odour  of  patchouli  diffused  in  it  is  30,  that  of 
lavender  60,  that  of  rosemary  74,  whilst  that  of  aniseed 
amounts  to  372.  It  would  be  idle  to  speculate  on  the 
quantities  of  matter  concerned  in  these  actions. 


12.  Aqueous  Vapour  in  relation  to  the  Terrestrial 
Temperatures. 

We  are  now  fully  prepared  for  a  result  which,  without 
such  preparation,  might  appear  incredible.  Water  is,  to 
some  extent,  a  volatile  body,  and  our  atmosphere,  resting 


50  FRAGMENTS   OF   SCIENCE. 

as  it  does  upon  the  surface  of  the  ocean,  receives  from  it 
a  continual  supply  of  aqueous  vapour.  It  would  be  an 
error  to  confound  clouds  or  fog  or  any  visible  mist  with 
the  vapour  of  water :  this  vapour  is  a  perfectly  impal- 
pable gas,  diffused,  even  on  the  clearest  days,  throughout 
the  atmosphere.  Compared  with  the  great  body  of  the 
air,  the  aqueous  vapour  it  contains  is  of  almost  infini- 
tesimal amount,  99^  out  of  every  100  parts  of  the  atmo- 
sphere being  composed  of  oxygen  and  nitrogen.  In  the 
absence  of  experiment,  we  should  never  think  of  ascribing 
to  this  scant  and  varying  constituent  any  important  in- 
fluence on  terrestrial  radiation ;  and  yet  its  influence  is 
far  more  potent  than  that  of  the  great  body  of  the  air. 
To  say  that  on  a  day  of  average  humidity  in  England, 
the  atmospheric  vapour  exerts  100  times  the  action  of 
the  air  itself,  would  certainly  be  an  understatement  of  the 
fact.  The  peculiar  qualities  of  this  vapour,  and  the  cir- 
cumstance that  at  ordinary  temperatures  it  is  very  near  its 
point  of  condensation,  render  the  results  which  it  yields 
in  the  apparatus  already  described,  less  than  the  truth  ; 
and  I  am  not  prepared  to  say  that  the  absorption  by  this 
substance  is  not  200  times  that  of  the  air  in  which  it  is 
diffused.  Comparing  a  single  molecule  of  aqueous  vapour 
with  an  atom  of  either  of  the  main  constituents  of  our 
atmosphere,  I  am  not  prepared  to  say  how  many  thou- 
sand times  the  action  of  the  former  exceeds  that  of  the 
latter. 

But  it  must  be  borne  in  mind  that  these  large 
numbers  depend,  in  part,  on  the  extreme  feebleness  of 
the  air  ;  the  power  of  aqueous  vapour  seems  vast,  because 
that  of  the  air  with  which  it  is  compared  is  infinitesimal. 
Absolutely  considered,  however,  this  substance,  notwith- 
standing its  small  specific  gravity,  exercises  a  very  potent 
action.  Probably  from  10  to  15  per  cent,  of  the  heat 
radiated  from  the  earth  is  absorbed  within  10  or  20  feet  of 


RADIATION.  67 

the  earth's  surface.  This  must  evidently  be  of  the  utmost 
consequence  to  the  life  of  the  world.  Imagine  the  super- 
ficial molecules  of  the  earth  trembling  with  the  motion  of 
heat,  and  imparting  it  to  the  surrounding  aether ;  this 
motion  would  be  carried  rapidly  away,  and  lost  for  ever  to 
our  planet,  if  the  waves  of  aether  had  nothing  but  the  air 
to  contend  with  in  their  outward  course.  But  the  aqueous 
vapour  takes  up  the  motion  of  the  aethereal  waves,  and 
becomes  thereby  heated,  thus  wrapping  the  earth  like  a 
warm  garment,  and  protecting  its  surface  from  the  deadly 
chill  which  it  would  otherwise  sustain.  Various  philo- 
sophers have  speculated  on  the  influence  of  an  atmospheric 
envelope.  De  Saussure,  Fourier,  M.  Pouillet  and  Mr. 
Hopkins  have,  one  and  all,  enriched  scientific  literature 
with  contributions  on  this  subject,  but  the  considerations 
which  these  eminent  men  have  applied  to  atmospheric  air, 
have,  if  my  experiments  be  correct,  to  be  transferred  to 
the  aqueous  vapour. 

The  observations  of  meteorologists  furnish  important, 
though  hitherto  unconscious,  evidence  of  the  influence  of 
this  agent.  Wherever  the  air  is  dry  we  are  liable  to 
daily  extremes  of  temperature.  By  day,  in  such  places, 
the  sun's  heat  reaches  the  earth  unimpeded,  and  renders 
the  maximum  high  ;  by  night,  on  the  other  hand,  the 
earth's  heat  escapes  unhindered  into  space,  and  renders  the 
minimum  low.  Hence  the  difference  between  the  maxi- 
mum and  minimum  is  greatest  where  the  air  is  driest. 
In  the  plains  of  India,  on  the  heights  of  the  Himalaya, 
in  central  Asia,  in  Australia — wherever  drought  reigns, 
we  have  the  heat  of  day  forcibly  contrasted  with  the  chill 
of  night.  In  the  Sahara  itself,  when  the  sun's  rays  cease 
to  impinge  on  the  burning  soil,  the  temperature  runs 
rapidly  down  to  freezing,  because  there  is  no  vapour  over- 
head to  check  the  calorific  drain.  And  here  another 
instance  might  be  added  to  the  numbers  already  known, 


68  FRAGMENTS   OF   SCIENCE. 

in  which  nature  tends  as  it  were  to  check  her  own  excess. 
By  nocturnal  refrigeration,  the  aqueous  vapour  of  the  air 
is  condensed  to  water  on  the  surface  of  the  earth  ;  and,  as 
only  the  superficial  portions  radiate,  the  act  of  condensa- 
tion makes  water  the  radiating  body.  Now  experiment 
proves  that  to  the  rays  emitted  by  water,  aqueous  vapour 
is  especially  opaque.  Hence  the  very  act  of  condensation, 
consequent  on  terrestrial  cooling,  becomes  a  safeguard  to 
the  earth,  imparting  to  its  radiation  that  particular  cha- 
racter which  renders  it  most  liable  to  be  prevented  from 
escaping  into  space. 

It  might  however  be  urged  that,  inasmuch  as  we 
Derive  all  our  heat  from  the  sun,  the  selfsame  covering 
which  protects  the  earth  from  chill  must  also  shut  out 
the  solar  radiation.  This  is  partially  true,  but  only 
partially  ;  the  sun's  rays  are  different  in  quality  from  the 
earth's  rays,  and  it  does  not  at  all  follow  that  the  sub- 
stance which  absorbs  the  one  must  necessarily  absorb 
the  other.  Through  a  layer  of  water,  for  example,  one 
tenth  of  an  inch  in  thickness,  the  sun's  rays  are  trans- 
mitted with  comparative  freedom ;  but  through  a  layer 
half  this  thickness,  as  Melloni  has  proved,  no  single  ray 
from  the  warmed  earth  could  pass.  In  like  manner,  the 
sun's  rays  pass  with  comparative  freedom  through  the 
aqueous  vapour  of  the  air :  the  absorbing  power  of  this 
substance  being  mainly  exerted  upon  the  heat  that 
endeavours  to  escape  from  the  earth.  In  consequence  of 
this  differential  action  upon  solar  and  terrestrial  heat,  the 
mean  temperature  of  our  planet  is  higher  than  is  due  to 
its  distance  from  the  sun. 


RADIATION.  59 


13.   Liquids  and  their  Vapours  in  relation  to 
Radiant  Heat. 

The  deportment  here  assigned  to  atmospheric  vapoui 
nas  been  established  by  direct  experiments  on  air  taken 
from  the  streets  and  parks  of  London,  from  the  downs  of 
Epsom,  from  the  hills  and  sea-beach  of  the  Isle  of  Wight, 
and  also  by  experiments  on  air  in  the  first  instance  dried, 
and  afterwards  rendered  artificially  humid  by  pure  dis- 
tilled water.  It  has  also  been  established  in  the  following 
way  :  Ten  volatile  liquids  were  taken  at  random  and  the 
power  of  these  liquids,  at  a  common  thickness,  to  inter- 
cept the  waves  of  heat,  was  carefully  determined.  The 
vapours  of  the  liquids  were  next  taken,  in  quantities  pro- 
portional to  the  quantities  of  liquid,  and  the  power  of  the 
vapours  to  intercept  the  waves  of  heat  was  also  deter- 
mined. Commencing  with  the  substance  which  exerted 
the  least  absorptive  power,  and  proceeding  onwards  to  the 
most  energetic,  the  following  order  of  absorption  was  ob- 
served : — 

Liquids  Vapours 

Bisulphide  of  carbon.  Bisulphide  of  carbon. 

Chloroform.  Chloroform.     - 

Iodide  of  methyl.  Iodide  of  methyl. 

Iodide  of  ethyl.  Iodide  of  ethyl. 

Benzol.  Benzol. 

Amylene.  Amylene. 

Sulphuric  ether.  Sulphuric  ether. 

Acetic  ether.  Acetic  ether. 

Formic  ether.  Formic  ether. 

Alcohol.  Alcohol. 
Water. 

We  here  find  the  order  of  absorption  in  both  cases  to 
be  the  same.  We  have  liberated  the  molecules  from  the 
bonds  which  trammel  them  more  or  less  in  a  liquid  condi- 
tion ;  but  this  change  in  their  state  of  aggregation  does 
not  change  their  relative  powers  of  absorption.  Nothing 


GO  j-RAGMENTS   OF   SCIENCE. 

could  more  clearly  prove  that  the  act  of  absorption  de- 
pends upon  the  individual  molecule,  which  equally  asserts 
its  power  in  the  liquid  and  the  gaseous  state.  We  may 
assuredly  conclude  from  the  above  table  that  the  position 
of  a  vapour  is  determined  by  that  of  its  liquid.  Now  at 
the  very  foot  of  the  list  of  liquids  stands  water,  signalising 
itself  above  all  others  by  its  enormous  power  of  absorption. 
And  from  this  fact,  even  if  no  direct  experiment  on  the 
vapour  of  water  had  ever  been  made,  we  should  be  en- 
titled to  rank  that  vapour  as  our  most  powerful  absorber 
of  radiant  heat.  Its  attenuation,  however,  diminishes  its 
action.  It  has  been  proved  that  a  shell  of  air  two  inches 
in  thickness  surrounding  our  planet,  and  saturated  with  the 
vapour  of  sulphuric  ether,  would  intercept  35  per  cent,  of 
the  earth's  radiation.  And  though  the  quantity  of  aqueous 
vapour  necessary  to  saturate  air  is  much  less  than  the 
amount  of  sulphuric  ether  vapour  which  it  can  sustain,  it 
is  still  extremely  probable  that  the  estimate  already  made 
of  the  action  of  atmospheric  vapour  within  10  feet  of 
the  earth's  surface,  is  under  the  mark ;  and  that  we  are 
indebted  to  this  wonderful  substance,  to  an  extent  not 
accurately  determined,  but  certainly  far  beyond  what  has 
hitherto  been  imagined,  for  the  temperature  now  existing 
at  the  surface  of  the  globe. 


14.  Reciprocity  of  Radiation  and  Absorption. 

Throughout  the  reflections  which  have  hitherto  occu- 
pied us,  the  image  before  the  mind  has  been  that  of  a 
radiant  source  generating  calorific  waves,  which  on  passing 
among  the  scattered  molecules  of  a  gas  or  vapour  were 
intercepted  by  those  molecules  in  various  degrees.  In 
all  cases  it  was  -the  transference  of  motion  from  the  aether 
to  the  comparatively  quiescent  molecules  of  the  gas  or 


EADIAT10N.  (31 

vapour.  We  have  now  to  change  the  form  of  our  concep- 
tion, and  to  figure  these  molecules  not  as  absorbers  but  as 
radiators,  not  as  the  recipients  but  as  the  originators  of 
wave-motion.  That  is  to  say,  we  must  figure  them  vibra- 
ting, and  generating  in  the  surrounding  aether  undulations 
which  speed  through  it  with  the  velocity  of  light.  Our 
object  now  is  to  enquire  whether  the  act  of  chemical  com- 
bination, which  proves  so  potent  as  regards  the  phenomena 
of  absorption,  does  not  also  manifest  its  power  in  the 
phenomena  of  radiation.  For  the  examination  of  this 
question  it  is  necessary,  in  the  first  place,  to  heat  our  gases 
and  vapours  to  the  same  temperature,  and  then  examine 
their  power  of  discharging  the  motion  thus  imparted  to 
them  upon  the  aether  in  which  they  swing. 

A  heated  copper  ball  was  placed  above  a  ring  gas- 
burner,  possessing  a  great  number  of  small  apertures,  the 
burner  being  connected  by  a  tube  with  vessels  containing 
the  various  gases  to  be  examined.  By  gentle  pressure 
the  gases  were  forced  through  the  orifices  of  the  burner 
against  the  copper  ball,  where  each  of  them,  being  heated, 
rose  in  an  ascending  column.  A  thermo-electric  pile, 
entirely  screened  off  from  the  hot  ball,  was  exposed  to  the 
radiation  of  the  warm  gas,  and  while  deflection  of  a 
magnetic  needle  connected  with  the  pile  declared  the 
energy  of  the  radiation. 

By  this  mode  of  experiment  it  was  proved  that  the 
selfsame  molecular  arrangement  which  renders  a  gas  a 
powerful  absorber,  renders  it  in  the  same  degree  a  power- 
ful radiator — that  the  atom  or  molecule  which  is  com- 
petent to  intercept  the  calorific  waves  is,  in  the  same 
degree,  competent  to  generate  them.  Thus,  while  the 
atoms  of  elementary  gases  proved  themselves  unable  to 
emit  any  sensible  amount  of  radiant  heat,  the  molecules 
of  compound  gases  were  shown  to  be  capable  of  power- 
fully disturbing  the  surrounding  aether.  By  special  modes 


32  FRAGMENTS    OF   SCIENCE. 

of  experiment  the  same  was  proved  to  hold  good  for  the 
vapours  of  volatile  liquids,  the  radiative  power  of  every 
vapour  being  found  proportional  to  its  absorptive  power. 

The  method  of  experiment  here  pursued,  though  not 
of  the  simplest  character,  is  still  within  your  grasp.  When 
air  is  permitted  to  rush  into  an  exhausted  tube,  the  tem- 
perature of  the  air  is  raised  to  a  degree  equivalent  to  the 
vis  viva  extinguished.1  Such  air  is  said  to  be  dynami- 
cally heated,  and,  if  pure,  it  shows  itself  incompetent  to 
radiate,  even  when  a  rock-salt  window  is  provided  for  the 
passage  of  its  rays.  But  if  instead  of  being  empty  the 
tube  contain  a  small  quantity  of  vapour,  then  the  warmed 
air  will  communicate  heat  by  contact  to  the  vapour, 
which  will  be  thus  enabled  to  radiate.  Thus  the  molecules 
of  the  vapour  convert  into  the  radiant  form  the  heat 
imparted  dynamically  to  the  atoms  of  the  air.  By  this 
process,  which  I  have  called  Dynamic  Radiation,  the 
radiative  power  of  both  vapours  and  gases  has  been  de- 
termined, and  the  reciprocity  of  their  radiation  and  ab- 
sorption proved.2 

In  the  excellent  researches  of  Leslie,  De  la  Provostaye 
and  Desains,  and  Balfour  Stewart,  the  reciprocity  of 
radiation  and  absorption,  as  regards  solid  bodies,  has  been 
variously  illustrated ;  while  the  labours,  theoretical  and 
experimental,  of  Kirchhoff  have  given  this  subject  a 
wonderful  expansion,  and  enriched  it  by  applications  of 
the  highest  kind.  To  their  results  are  now  to  be  added 
the  foregoing,  whereby  gases  and  vapours,  which  have 
been  hitherto  thought  inaccessible  to  experiments  of  this 
kind,  are  proved  to  exhibit  the  duality  of  radiation  and 


1  See  page  14  for  a  definition  of  vis  viva. 

2  When  heated  air  imparts  its  motion  to  another  gas  or  vapour,  the 
transference  of  heat  is  accompanied  by  a  change  of  vibrating  period.     The 
Dynamic  Badiation  cf  vapours  is  rendered  possible  by  the  transmutation  of 
vibrations. 


KADIATION.  63 

absorption,  the  influence  of  chemical  combination  on  both 
being  exhibited  in  the  most  decisive  and  extraordinary 
way. 

1 5.  Influence  of  Vibrating  Period  and  Molecular  .Form. 
Physical  Analysis  of  the  Human  Breath. 

In  the  foregoing  experiments  with  gases  and  vapours 
we  have  employed  throughout  invisible  rays :  some  of 
these  bodies  are  so  impervious,  that  in  lengths  of  a  few 
feet  only  they  intercept  every  ray  as  effectually  as  a 
layer  of  pitch  would  do.  The  substances,  however,  which 
show  themselves  thus  opaque  to  radiant  heat  are  perfectly 
transparent  to  light.  Now  the  rays  of  light  differ  from 
those  of  invisible  heat,  only  in  point  of  period,  the  former 
failing  to  affect  the  retina  because  their  periods  of  recur- 
rence are  too  slow.  Hence,  in  some  way  or  other  the 
transparency  of  our  gases  and  vapours  depends  upon  the 
periods  of  the  waves  which  impinge  upon  them.  What 
is  the  nature  of  this  dependence  ?  The  admirable  re- 
searches of  Kirchhoff  help  us  to  an  answer.  The  atoms 
and  molecules  of  every  gaa  have  certain  definite  rates  of 
oscillation,  and  those  waves  of  aether  are  most  copiously 
absorbed  whose  periods  of  recurrence  synchronise  with 
the  periods  of  the  molecules  amongst  which  they  pass. 
Thus,  when  we  find  the  invisible  rays  absorbed  and  the 
visible  ones  transmitted  by  a  layer  of  gas,  we  conclude 
that  the  oscillating  periods  of  the  gaseous  molecules  co- 
incide with  those  of  the  invisible,  and  not  with  those  of 
the  visible  spectrum. 

It  requires  some  discipline  of  the  imagination  to  form 
a  clear  picture  of  this  process.  Such  a  picture  is,  however, 
possible,  and  ought  to  be  obtained.  When  the  waves  of 
aether  impinge  upon  molecules  whose  periods  of  vibration 
coincide  with  the  recurrence  of  the  undulations,  the  timed 


64  FRAGMENTS   OP  SCIENCE. 

strokes  of  the  waves,  the  vibration  of  the  molecules 
augments,  as  a  heavy  pendulum  is  set  in  motion  by  well- 
timed  puffs  of  breath.  Millions  of  millions  of  shocks  are 
received  every  second  from  the  calorific  waves ;  and  it  is 
not  difficult  to  see  that  as  every  wave  arrives  just  in  time 
to  repeat  the  action  of  its  predecessor,  the  molecules  must 
finally  be  caused  to  swing  through  wider  spaces  than  if 
the  arrivals  were  not  so  timed.  In  fact,  it  is  not  difficult 
to  see  that  an  assemblage  of  molecules,  operated  upon  by 
contending  waves,  might  remain  practically  quiescent. 
This  is  actually  the  case  when  the  waves  of  the  visible 
spectrum  pass  through  a  transparent  gas  or  vapour.  There 
is  here  no  sensible  transference  of  motion  from  the  aether 
to  the  molecules ;  in  other  words,  there  is  no  sensible  ab- 
sorption of  heat. 

One  striking  example  of  the  influence  of  period  may 
be  here  recorded.  Carbonic  acid  gas  is  one  of  the  feeblest 
of  absorbers  of  the  radiant  heat  emitted  by  solid  sources. 
It  is,  for  example,  to  a  great  extent  transparent  to  the  rays 
emitted  by  the  heated  copper  plate  already  referred  to. 
There  are,  however,  certain  rays,  comparatively  few  in 
number,  emitted  by  the  copper,  to  which  the  carbonic 
acid  is  impervious ;  and  could  we  obtain  a  source  of  heat 
emitting  such  rays  only,  we  should  find  carbonic  acid 
more  opaque  to  the  radiation  from  that  source,  than 
any  other  gas.  Such  a  source  is  actually  found  in  the 
Hume  of  carbonic  oxide,  where  hot  carbonic  acid  con- 
stitutes the  main  radiating  body.  Of  the  rays  emitted 
by  our  heated  plate  of  copper,  olefiant  gas  absorbs  ten 
times  the  quantity  absorbed  by  carbonic  acid.  Of  the 
rays  emitted  by  a  carbonic  oxide  flame,  carbonic  acid 
absorbs  twice  as  much  as  olefiant  gas.  This  wonderful 
change  in  the  power  of  the  former,  as  an  absorber,  is  simply 
due  to  the  fact,  that  the  periods  of  the  hot  and  cold 
carbonic  acid  are  identical,  and  that  the  waves  from  the 


RADIATION.  66 

flame  freely  transfer  their  motion  to  the  molecules  which 
synchronise  with  them.  Thus  it  is  that  the  tenth  of  an 
atmosphere  of  carbonic  acid,  enclosed  in  a  tube  four  feet 
long,  absorbs  60  per  cent,  of  the  radiation  from  a  carbonic 
oxide  flame,  while  one-thirtieth  of  an  atmosphere  absorbs 
48  per  cent,  of  the  heat  from  the  same  origin. 

In  fact,  the  presence  of  the  minutest  quantity  of  car- 
bonic acid  may  be  detected  by  its  action  on  the  rays 
from  the  carbonic  oxide  flame.  Carrying,  for  example, 
the  dried  human  breath  into  a  tube  four  feet  long,  the 
absorption  there  effected  by  the  carbonic  acid  of  the 
breath  amounts  to  50  per  cent,  of  the  entire  radiation. 
Badiant  heat  may  indeed  be  employed  as  a  means  of 
determining  practically  the  amount  of  carbonic  acid 
expired  from  the  lungs.  My  late  assistant,  Mr.  Barrett, 
while  under  my  direction,  made  this  determination.  The 
absorption  produced  by  the  breath  freed  from  its  moisture, 
but  retaining  its  carbonic  acid,  was  first  determined.  Car- 
bonic acid,  artificially  prepared,  was  then  mixed  with  dry 
air  in  such  proportions  that  the  action  of  the  mixture  upon 
the  rays  of  heat  was  the  same  as  that  of  the  dried  breath. 
The  percentage  of  the  former  being  known,  immediately 
gave  that  of  the  latter.  The  same  breath  analysed  che- 
mically by  Dr.  Frankland,  and  physically  by  Mr.  Barrett, 
gave  the  following  results  : — 

Percentage  of  Carbonic  Acid  in  the  Human  Breath. 

Chemical  analysis  Physical  analysis 

4-66 4-56 

fl-33 5-22 

It  is  thus  proved  that  in  the  quantity  of  aethereal 
motion  which  it  is  competent  to  take  up,  we  have  a 
practical  measure  of  the  carbonic  acid  of  the  breath,  and 
hence  of  the  combustion  going  on  in  the  human  lungs. 

Still  this  question  of  period,  though  of  the  utmost 


30  FRAGMENTS    OF   SCIENCE. 

importance,  is  not  competent  to  account  for  the  whole 
of  the  observed  facts.  The  aether,  as  far  as  we  know, 
accepts  vibrations  of  all  periods  with  the  same  readiness. 
To  it  the  oscillations  of  an  atom  of  oxygen  are  just  as 
acceptable  as  those  of  a  molecule  of  olefiant  gas ;  that 
the  vibrating  oxygen  then  stands  so  far  below  the  olefiant 
gas  in  radiant  power  must  be  referred  not  to  period,  but 
to  some  other  peculiarity  of  the  elementary  gas.  The 
atomic  group  which  constitutes  the  molecule  of  olefiant 
gas,  produces  many  thousand  times  the  disturbance  caused 
by  the  oxygen,  because  the  group  is  able  to  lay  a  vastly 
more  powerful  hold  upon  the  aether  than  the  single  atoms 
can.  The  cavities  and  indentations  of  a  molecule  com- 
posed of  spherical  atoms  may  be  one  cause  of  this  aug- 
mented hold.  Another,  and  probably  very  potent  one  may 
be,  that  the  vibrations,  being  those  of  the  constituent 
atoms  of  the  molecule,  are  generated  in  highly  condensed 
aether,  which  acts  like  condensed  air  upon  sound.  But 
whatever  may  be  the  fate  of  these  attempts  to  visualise 
the  physics  of  the  process,  it  will  still  remain  true,  that  to 
account  for  the  phenomena  of  radiation  and  absorption 
we  must  take  into  consideration  the  shape,  size,  and  con- 
dition of  the  aether  within  the  molecules,  by  which  the 
aether  is  disturbed. 


1 6.  Summaiy  an  I  Conclusion. 

Let  us  now  cast  a  momentary  glance  over  the  ground 
that  we  have  left  behind.  The  general  nature  of  light 
and  heat  was  first  briefly  described  :  the  compounding  of 
matter  from  elementary  atoms,  and  the  influence  of  the 
act  of  combination  on  radiation  and  absorption,  were 
considered  and  experimentally  illustrated.  Through  the 
transparent  elementary  gases  radiant  heat  was  found  to 
pass  as  through  a  vacuum,  while  many  of  the  compound 


RADIATION.  67 

gases  presented  almost  impassable  obstacles  to  the  calorific 
waves.  This  deportment  of  the  simple  gases  directed  our 
attention  to  other  elementary  bodies,  the  examination 
of  which  led  to  the  discovery  that  the  element  iodine, 
dissolved  in  bisulphide  of  carbon,  possesses  the  power 
of  detaching,  with  extraordinary  sharpness,  the  light  of 
the  spectrum  from  its  heat,  intercepting  all  luminous 
rays  up  to  the  extreme  red,  and  permitting  the  calorific 
rays  beyond  the  red  to  pass  freely  through  it.  This  sub- 
stance was  then  employed  to  filter  the  beams  of  the  electric 
light,  and  to  form  foci  of  invisible  rays  so  intense  as  to 
produce  almost  all  the  effects  obtainable  in  an  ordinary 
fire.  Combustible  bodies  were  burnt,  and  refractory  ones 
were  raised  to  a  white  heat,  by  the  concentrated  invisible 
rays.  Thus,  by  exalting  their  refrangibility,  the  invisible 
rays  of  the  electric  light  were  rendered  visible,  and  all  the 
colours  of  the  solar  spectrum  were  extracted  from  utter 
darkness.  The  extreme  richness  of  the  electric  light  in 
invisible  rays  of  low  refrangibility  was  demonstrated,  one- 
eighth  only  of  its  radiation  consisting  of  luminous  rays. 
The  deadness  of  the  optic  nerve  to  those  invisible  rays 
was  proved,  and  experiments  were  then  added  to  show  that 
the  bright  and  the  dark  rays  of  a  solid  body,  raised  gradu- 
ally to  intense  incandescence,  are  strengthened  together; 
intense  dark  heat  being  an  invariable  accompaniment  of 
intense  white  heat.  A  sun  could  not  be  formed,  or  a 
meteorite  rendered  luminous,  on  any  other  condition.  The 
light-giving  rays  constituting  only  a  small  fraction  of  the 
total  radiation,  their  unspeakable  importance  to  us  is  due 
to  the  fact,  that  their  periods  are  attuned  to  the  special 
requirements  of  the  eye. 

Among  the  vapours  of  volatile  liquids  vast  differences 
were  also  found  to  exist,  as  regards  their  powers  of 
absorption.  "We  followed  various  molecules  from  a  state 
of  liquid  to  a  state  of  gas,  and  found,  in  both  states  of 


88  FRAGMENTS   OF   SCIENCE. 

aggregation,  the  power  of  the  individual  molecules 
equally  asserted.  The  position  of  a  vapour  as  an  absorber 
of  radiant  heat  was  shown  to  be  determined  by  that  of 
the  liquid  from  which  it  is  derived.  Reversing  our  con- 
ceptions, and  regarding  the  molecules  of  gases  and  vapours 
not  as  the  recipients  but  as  the  originators  of  wave- 
motion  ;  not  as  absorbers  but  as  radiators ;  it  was  proved 
that  the  powers  of  absorption  and  radiation  went  hand  in 
hand,  the  selfsame  chemical  act  which  rendered  a  body 
competent  to  intercept  the  waves  of  aether,  rendering  it 
competent,  in  the  same  degree,  to  generate  them.  Per- 
fumes were  next  subjected  to  examination,  and,  notwith- 
standing their  extraordinary  tenuity,  they  were  found 
vastly  superior,  in  point  of  absorptive  power,  to  the  body 
of  the  air  in  which  they  were  diffused.  We  were  led  thus 
slowly  up  to  the  examination  of  the  most  widely  diffused 
and  most  important  of  all  vapours — the  aqueous  vapour 
of  our  atmosphere,  and  we  found  in  it  a  potent  absorber 
of  the  purely  calorific  rays.  The  power  of  this  substance 
to  influence  climate,  and  its  general  influence  on  the 
temperature  of  the  earth,  were  then  briefly  dwelt  upon. 
A  cobweb  spread  above  a  blossom  is  sufficient  to  protect  it 
from  nightly  chill ;  and  thus  the  aqueous  vapour  of  our 
air,  attenuated  as  it  is,  checks  the  drain  of  terrestrial  heat, 
and  saves  the  surface  of  our  planet  from  the  refrigeration 
which  would  assuredly  accrue,  were  no  such  substance  in- 
terposed between  it  and  the  voids  of  space.  We  considered 
the  influence  of  vibrating  period,  and  molecular  form,  on 
absorption  and  radiation,  and  finally  deduced,  from  its 
action  upon  radiant  heat,  the  exact  amount  of  carbonic 
acid  expired  by  the  human  lungs. 

Thus,  in  brief  outline,  were  placed  before  you  some  of 
the  results  of  recent  enquiries  in  the  domain  of  Radiation, 
and  my  aim  throughout  has  been  to  raise  in  your  minds 
distinct  physical  images  of  the  various  processes  involved 


RADIATION.  69 

in  our  researches.  It  is  thought  by  some  that  natural 
science  has  a  deadening  influence  on  the  imagination,  and 
a  doubt  might  fairly  be  raised  as  to  the  value  of  any 
study  which  would  necessarily  have  this  effect.  But  the 
experience  of  the  last  hour  must,  I  think,  have  convinced 
you,  that  the  study  of  natural  science  goes  hand  in  hand 
with  the  culture  of  the  imagination.  Throughout  the 
greater  part  of  this  discourse  we  have  been  sustained  by 
this  faculty.  We  have  been  picturing  atoms,  and  mole- 
cules, and  vibrations,  and  waves,  which  eye  has  never 
seen  nor  ear  heard,  and  which  can  only  be  discerned  by 
the  exercise  of  imagination.  This,  in  fact,  is  the  faculty 
which  enables  us  to  transcend  the  boundaries  of  sense, 
and  connect  the  phenomena  of  our  visible  world  with 
those  of  an  invisible  one.  Without  imagination  we  never 
could  have  risen  to  the  conceptions  which  have  occupied 
us  here  to-day ;  and  in  proportion  to  your  power  of  exer- 
cising this  faculty  aright,  and  of  associating  definite  mental 
images  with  the  terms  employed,  will  be  the  pleasure 
and  the  profit  which  you  will  derive  from  this  lecture. 
The  outward  facts  of  nature  are  insufficient  to  satisfy  the 
mind.  We  cannot  be  content  with  knowing  that  the  light 
and  heat  of  the  sun  illuminate  and  warm  the  world.  We 
are  led  irresistibly  to  enquire,  *  What  is  light,  and  what  is 
heat  ? '  and  this  question  leads  us  at  once  out  of  the  region 
of  sense  into  that  of  imagination. 

Thus  pondering,  and  questioning,  and  striving  to  sup- 
plement that  which  is  felt  and  seen,  but  which  is  incom- 
plete, by  something  unfelt  and  unseen  which  is  necessary 
to  its  completeness,  men  of  genius  have  in  part  discerned, 
not  only  the  nature  of  light  and  heat,  but  also,  through 
them,  the  general  relationship  of  natural  phenomena.  The 
working  power  of  Nature  is  the  power  of  actual  or  poten- 
tial motion,  of  which  all  its  phenomena  are  but  special 
forms.  This  motion  manifests  itself  in  tangible  and  in 


70  FRAGMENTS   OF   SCIENCE. 

intangible  matter,  being  incessantly  transferred  from  the 
one  to  the  other,  and  incessantly  transformed  by  the 
change.  It  is  as  real  in  the  waves  of  the  aether  as  in  the 
waves  of  the  sea ;  the  latter — derived  as  they  are  from  winds, 
which  in  their  turn  are  derived  from  the  sun — are,  indeed, 
nothing  more  than  the  heaped-up  motion  of  the  former. 
It  is  the  calorific  waves  emitted  by  the  sun  which  heat  our 
air,  produce  our  winds,  and  hence  agitate  our  ocean.  And 
whether  they  break  in  foam  upon  the  shore,  or  rub  silently 
against  the  ocean's  bed,  or  subside  by  the  mutual  friction 
of  their  own  parts,  the  sea  waves,  which  cannot  subside 
without  producing  heat,  finally  resolve  themselves  into 
waves  of  aether,  thus  regenerating  the  motion  from  which 
their  temporary  existence  was  derived.  This  connection 
is  typical.  Nature  is  not  an  aggregate  of  independent 
parts,  but  an  organic  whole.  If  you  open  a  piano  and 
sing  into  it,  a  certain  string  will  respond.  Change  the 
pitch  of  your  voice ;  the  first  string  ceases  to  vibrate,  but 
another  replies.  Change  again  the  pitch ;  the  first  two 
strings  are  silent,  while  another  resounds.  Now  in  alter- 
ing the  pitch  you  simply  change  the  form  of  the  motion 
communicated  by  your  vocal  chords  to  the  air,  one  string 
responding  to  one  form,  and  another  to  another.  And 
thus  is  sentient  man  acted  on  by  Nature,  the  optic,  the 
auditory,  and  other  nerves  of  the  human  body  being  so 
many  strings  differently  tuned,  and  responsive  to  different 
forms  of  the  universal  power. 


III. 

ON  RADIANT  HEAT  IN  RELATION  TO  THE  COLOUR 
AND  CHEMICAL  CONSTITUTION  OF  BODIES, 

1866. 

ONE  of  the  most  important  functions  of  physical  science, 
considered  as  a  discipline  of  the  mind,  is  to  enable  us 
by  means  of  the  tangible  processes  of  Nature  to  apprehend 
the  intangible.  The  tangible  processes  give  direction  to 
the  line  of  thought ;  but  this  once  given,  the  length  of 
the  line  is  not  limited  by  the  boundaries  of  the  senses. 
Indeed,  the  domain  of  the  senses,  in  Nature,  is  almost  in- 
finitely small  in  comparison  with  the  vast  region  accessible 
to  thought  which  lies  beyond  them.  From  a  few  observa- 
tions of  a  comet,  when  it  comes  within  the  range  of  his 
telescope,  an  astronomer  can  calculate  its  path  in  regions 
which  no  telescope  can  reach :  and  in  like  manner,  by 
means  of  data  furnished  in  the  narrow  world  of  the  senses, 
we  make  ourselves  at  home  in  other  and  wider  worlds, 
which  can  be  traversed  by  the  intellect  alone. 

From  the  earliest  ages  the  questions,  '  What  is  light  ?  ' 
and  '  What  is  heat  ? '  have  occurred  to  the  minds  of  men  ; 
but  these  questions  never  would  have  been  answered  had 
they  not  been  preceded  by  the  question,  '  What  is  sound  ? ' 
Amid  the  grosser  phenomena  of  acoustics  the  mind  was 
first  disciplined,  conceptions  being  thus  obtained  from 
direct  observation,  which  were  afterwards  applied  to  phe- 
nomena of  a  character  far  too  subtle  to  be  observed  directly. 
Sound  we  know  to  be  due  to  vibratory  motion.  A  vibrating 


72  FRAGMENTS  OF  SCIENCE. 

tuning-fork,  for  example,  moulds  the  air  around  it  into 
undulations  or  waves,  which  speed  away  on  all  sides  with 
a  certain  measured  velocity,  impinge  upon  the  drum  of 
the  ear,  shake  the  auditory  nerve,  and  awake  in  the  brain 
the  sensation  of  sound.  When  sufficiently  near  a  sounding 
body  we  can  feel  the  vibrations  of  the  air.  A  deaf  man, 
for  example,  plunging  his  hand  into  a  bell  when  it  is 
sounded,  feels  through  the  common  nerves  of  his  body 
those  tremors  which,  when  imparted  to  the  nerves  of 
healthy  ears,  are  translated  into  sound.  There  are  various 
ways  of  rendering  those  sonorous  vibrations  not  only 
tangible  but  visible  ;  and  it  was  not  until  numberless  ex- 
periments of  this  kind  had  been  executed,  that  the  scien- 
tific investigator  abandoned  himself  wholly,  and  without  a 
shadow  of  misgiving,  to  the  conviction  that  what  is  sound 
within  us  is,  outside  of  us,  a  motion  of  the  air. 

But  once  having  established  this  fact — once  having 
proved  beyond  all  doubt  that  the  sensation  of  sound  is 
produced  by  an  agitation  of  the  nerve  of  the  ear — the 
thought  soon  suggested  itself  that  light  might  be  due  to 
an  agitation  of  the  nerve  of  the  eye.  This  was  a  great 
step  in  advance  of  that  ancient  notion  which  regarded 
light  as  something  emitted  by  the  eye,  and  not  as  any- 
thing imparted  to  it.  But  if  light  be  produced  by  an 
agitation  of  the  optic  nerve  or  retina,  what  is  it  that  pro- 
duces the  agitation  ?  Newton,  you  know,  supposed  minute 
particles  to  be  shot  through  the  humours  of  the  eye  against 
the  retina,  which  he  supposed  to  hang  like  a  target  at  the 
back  of  the  eye.  The  impact  of  these  particles  against 
the  target,  Newton  believed  to  be  the  cause  of  light.  But 
Newton's  notion  has  not  held  its  ground,  being  entirely 
driven  from  the  field  by  the  more  wonderful  and  far  more 
philosophical  notion  that  light,  like  sound,  is  a  product 
of  wave-motion. 

The  domain  in  which  this  motion  of  light  is  carried  on 


RADIANT   HEAT  AND   ITS  RELATIONS.  73 

lies  entirely  beyond  the  reach  of  our  senses.  The  waves  of 
light  require  a  medium  for  their  formation  and  propaga- 
tion ;  but  we  cannot  see,  or  feel,  or  taste,  or  smell  this 
medium.  How,  then,  has  its  existence  been  established  ? 
By  showing,  that  by  the  assumption  of  this  wonderful  in- 
tangible aether,  all  the  phenomena  of  optics  are  accounted 
for,  with  a  fulness,  and  clearness,  and  collusiveness,  which 
leave  no  desire  of  the  intellect  unsatisfied.  When  the  law 
of  gravitation  first  suggested  itself  to  the  mind  of  Newton, 
what  did  he  do  ?  He  set  himself  to  examine  whether  it 
accounted  for  all  the  facts.  He  determined  the  courses 
of  the  planets ;  he  calculated  the  rapidity  of  the  moon's 
fall  towards  the  earth  ;  he  considered  the  precession  of  the 
equinoxes,  the  ebb  and  flow  of  the  tides,  and  found  all  ex- 
plained by  the  law  of  gravitation.  He  therefore  regarded 
this  law  as  established,  and  the  verdict  of  science  subse- 
quently confirmed  his  conclusion.  On  similar,  and,  if 
possible,  on  stronger  grounds,  we  found  our  belief  in  the 
existence  of  the  universal  aether.  It  explains  facts  far 
more  various  and  complicated  than  those  on  which  Newton 
based  his  law.  If  a  single  phenomenon  could  be  pointed 
out  which  the  aether  is  proved  incompetent  to  explain,  we 
should  have  to  give  it  up ;  but  no  such  phenomenon  has 
ever  been  pointed  out.  It  is,  therefore,  at  least  as  certain 
that  space  is  filled  with  a  medium,  by  means  of  which  suns 
and  stars  diffuse  their  radiant  power,  as  that  it  is  traversed 
by  that  force  which  holds  in  its  grasp,  not  only  our  plane- 
tary system,  but  the  immeasurable  heavens  themselves. 

There  is  no  more  wonderful  instance  than  this  of  the 
production  of  a  line  of  thought,  from  the  world  of  the  senses 
into  the  region  of  pure  imagination.  I  mean  by  imagination 
here,  not  that  play  of  fancy  which  can  give  to  airy  nothings 
a  local  habitation  and  a  name,  but  that  power  which 
enables  the  mind  to  conceive  realities  which  lie  beyond 
the  range  of  the  senses — to  present  to  itself  distinct 


74  FRAGMENTS   OF   SCIENCE. 

images  of  processes  which,  though  mighty  in  the  aggre- 
gate beyond  all  conception,  are  so  minute  individually  as 
to  elude  all  observation.  It  is  the  waves  of  air  excited 
by  a  tuning-fork  which  render  its  vibrations  audible. 
It  is  the  waves  of  aether  sent  forth  from  those  lamps  over- 
head which  render  them  luminous  to  us ;  but  so  minute 
are  these  waves,  that  it  would  take  from  30,000  to  60,000 
of  them  placed  end  to  end  to  cover  a  single  inch.  Their 
number,  however,  compensates  for  their  minuteness. 
Trillions  of  them  have  entered  your  eyes,  and  hit  the 
retina  at  the  back  of  the  eye,  in  the  time  consumed  in  the 
utterance  of  the  shortest  sentence  of  this  discourse.  This 
is  the  steadfast  result  of  modern  research  ;  but  we  never 
could  have  reached  it  without  previous  discipline.  We 
never  could  have  measured  the  waves  of  light,  nor  even 
imagined  them  to  exist,  had  we  not  previously  exercised 
ourselves  among  the  waves  of  sound.  Sound  and  light 
are  now  mutually  helpful,  the  conceptions  of  each  being 
expanded,  strengthened,  and  denned  by  the  conceptions  of 
the  other. 

The  aether  which  conveys  the  pulses  of  light  and  heat 
not  only  fills  celestial  space,  swathing  suns,  and  planets, 
and  moons,  but  it  also  encircles  the  atoms  of  which 
these  bodies  are  composed.  It  is  the  motion  of  these 
atoms,  and  not  that  of  any  sensible  parts  of  bodies,  that 
the  aether  conveys ;  it  is  this  motion  that  constitutes 
the  objective  cause  of  what,  in  our  sensations,  are  light 
and  heat.  An  atom,  then,  sending  its  pulses  through 
the  aether,  resembles  a  tuning-fork  sending  its  pulses 
through  the  air.  Let  us  look  for  a  moment  at  this  thrill- 
ing medium,  and  briefly  consider  its  relation  to  the  bodies 
whose  vibrations  it  conveys.  Different  bodies,  when  heated 
to  the  same  temperature,  possess  very  different  powers  of 
agitating  the  aether  :  some  are  good  radiators,  others  are 
bad  radiators ;  which  means  that  some  are  so  constituted 


RADIANT   HEAT   AND    ITS   RELATIONS.  75 

as  to  communicate  their  motion  freely  to  the  aether, 
producing  therein  powerful  undulations ;  while  others  are 
unable  thus  to  communicate  their  motion,  but  glide 
through  the  medium  without  materially  disturbing  its  re- 
pose. Eecent  experiments  have  proved  that  elementary 
bodies,  except  under  certain  anomalous  conditions,  belong 
to  the  class  of  bad  radiators.  An  atom,  vibrating  in  the 
aether,  resembles  a  naked  tuning-fork  vibrating  in  the  air. 
The  amount  of  motion  communicated  to  the  air  by  the  thin 
prongs  is  too  small  to  evoke  at  any  distance  the  sensation 
of  sound.  But  if  we  permit  the  atoms  to  combine  chemi- 
cally and  form  molecules,  the  result,  in  many  cases,  is  an 
enormous  change  in  the  power  of  radiation.  The  amount 
of  aethereal  disturbance,  produced  by  the  combined  atoms 
of  a  body,  may  be  many  thousand  times  that  produced  by 
its  constituent  atoms  when  uncombined.  The  effect  is 
roughly  typified  by  a  tuning-fork  when  connected  with 
its  resonant  case.  The  fork  and  its  case  swing  as  a 
compound  system,  and  the  vibrations  which  were  before 
inaudible,  are  now  the  source  of  a  musical  sound  so  power- 
ful, that  it  might  be  plainly  heard  by  thousands  at  once. 
The  fork  and  its  case  combined  may  be  roughly  regarded 
as  a  good  radiator  of  sound. 

The  pitch  of  a  musical  note  depends  upon  the  rapidity 
of  its  vibrations,  or,  in  other  words,  on  the  length  of  its 
waves.  Now,  the  pitch  of  a  note  answers  to  the  colour 
of  light.  Taking  a  slice  of  white  light  from  the  sun,  or 
from  an  electric  lamp,  and  causing  the  light  to  pass 
through  an  arrangement  of  prisms,  it  is  decomposed.  We 
have  the  effect  obtained  by  Newton,  who  first  unrolled 
the  solar  beam  into  the  splendours  of  the  solar  spectrum. 
At  one  end  of  this  spectrum  we  have  red  light,  at  the 
other,  violet;  and  between  those  extremes  lie  the  other 
prismatic  colours.  As  we  advance  along  the  spectrum 
from  the  red  to  the  violet,  the  pitch  of  the  light — if  I 


76  FRAGMENTS   OF   SCIENCE. 

may  use  the  expression — heightens,  the  sensation  of  violet 
being  produced  by  a  more  rapid  succession  of  impulses  than 
that  which  produces  the  impression  of  red.  The  vibrations 
of  the  violet  are  about  twice  as  rapid  as  those  of  the  red ;  in 
other  words,  the  range  of  the  visible  spectrum  is  about  an 
octave. 

There  is  no  solution  of  continuity  in  this  spectrum ; 
one  colour  changes  into  another  by  insensible  gradations. 
It  is  as  if  an  infinite  number  of  tuning-forks,  of  gradually 
augmenting  pitch,  were  vibrating  at  the  same  time.  But 
turning  to  another  spectrum — that,  namely,  obtained  from 
the  incandescent  vapour  of  silver — you  observe  that  it 
consists  of  two  narrow  and  intensely  luminous  green 
bands.  Here  it  is  as  if  two  forks  only,  of  slightly  different 
pitch,  were  vibrating.  The  length  of  the  waves  which 
produce  this  first  band  is  such  that  47,460  of  them,  placed 
end  to  end,  would  fill  an  inch.  The  waves  which  pro- 
duce the  second  band  are  a  little  shorter ;  it  would  take 
of  these  47,920  to  fill  an  inch.  In  the  case  of  the  first 
band,  the  number  of  impulses  imparted,  in  one  second,  to 
every  eye  which  sees  it,  is  577  millions  of  millions ; 
while  the  number  of  impulses  imparted,  in  the  same  time, 
by  the  second  band  is  600  millions  of  millions.  We 
may  project  upon  a  white  screen  the  beautiful  stream  of 
green  light  from  which  these  bands  were  derived.  This 
luminous  stream  is  the  incandescent  vapour  of  silver. 
The  rates  of  vibration  of  the  atoms  of  that  vapour  are  as 
rigidly  fixed  as  those  of  two  tuning-forks ;  and  to  what- 
ever height  the  temperature  of  the  vapour  may  be  raised, 
the  rapidity  of  its  vibrations,  and  consequently  its  colour, 
which  wholly  depends  upon  that  rapidity,  remain  un- 
changed. 

The  vapour  of  water,  as  well  as  the  vapour  of  silver, 
has  its  definite  periods  of  .vibration,  and  these  are  such  as 
to  disqualify  the  vapour  when  acting  freely  as  such,  from 


KADIANT  HEAT  AND   ITS  KELATIONS.  77 

being  raised  to  a  white  heat.  The  oxyhydrogen  flame,  for 
example,  consists  of  hot  aqueous  vapour.  It  is  scarcely 
visible  in  the  air  of  this  room,  and  it  would  be  still  less 
visible  if  we  could  burn  the  gas  in  a  clean  atmosphere. 
But  the  atmosphere,  even  at  the  summit  of  Mont  Blanc, 
is  dirty  ;  in  London  it  is  more  than  dirty  ;  and  the  burn- 
ing dirt  gives  to  this  flame  the  greater  portion  of  its 
present  light.  But  the  heat  of  the  flame  is  enormous. 
Cast  iron  fuses  at  a  temperature  of  2,000°  Fahr. ;  while 
the  temperature  of  the  oxyhydrogen  flame  is  6,000°  Fahr. 
A  piece  of  platinum  is  heated  to  vivid  redness,  at  a  distance 
of  two  inches  beyond  the  visible  termination  of  the  flame. 
The  vapour  which  produces  incandescence  is  here  abso- 
lutely dark.  In  the  flame  itself  the  platinum  is  raised  to 
dazzling  whiteness,  and  is  even  pierced  by  the  flame. 
When  this  flame  impinges  on  a  piece  of  lime,  we  have  the 
dazzling  Drummond  light.  But  the  light  is  here  due  to 
the  fact  that  when  it  impinges  upon  the  solid  body,  the 
vibrations  excited  in  that  body  by  the  flame  are  of  periods 
different  from  its  own. 

Thus  far  we  have  fixed  our  attention  on  atoms  and 
molecules  in  a  state  of  vibration,  and  surrounded  by  a 
medium  which  accepts  their  vibrations,  and  transmits  them 
through  space.  But  suppose  the  waves  generated  by  one 
system  of  molecules  to  impinge  upon  another  system,  how 
will  the  waves  be  affected?  Will  they  be  stopped,  or 
will  they  be  permitted  to  pass  ?  Will  they  transfer  their 
motion  to  the  molecules  on  which  they  impinge,  or  will 
they  glide  round  the  molecules,  through  the  intermole- 
cular  spaces,  and  thus  escape  ? 

The  answer  to  this  question  depends  upon  a  condition 
which  may  be  beautifully  exemplified  by  an  experiment 
on  sound.  These  two  tuning-forks  are  tuned  absolutely 
alike.  They  vibrate  with  the  same  rapidity,  and,  mounted 
thus  upon  their  resonant  cases,  you  hear  them  loudly 


78  FRAGMENTS   OF  SCIENCE. 

Bounding  the  same  musical  note.  Stopping  one  of  the 
forks,  I  throw  the  other  into  strong  vibration,  and  bring 
that  other  near  the  silent  fork,  but  not  into  contact  with 
it.  Allowing  them  to  continue  in  this  position  for  four 
or  five  seconds,  and  then  stopping  the  vibrating  fork, 
the  sound  has  not  ceased.  The  second  fork  has  taken  up 
tho  vibrations  of  its  neighbour,  and  is  now  sounding  in  its 
turn.  Dismounting  one  of  the  forks,  and  permitting  the 
other  to  remain  upon  its  stand,  I  throw  the  dismounted 
fork  into  strong  vibration.  You  cannot  hear  it  sound. 
Detached  from  its  stand,  the  amount  of  motion  which  it 
can  communicate  to  the  air  is  too  small  to  be  sensible 
at  any  distance.  When  the  dismounted  fork  is  brought 
close  to  the  mounted  one,  but  not  into  actual  contact  with 
it,  out  of  the  silence  rises  a  mellow  sound.  Whence  comes 
it  ?  From  the  vibrations  which  have  been  transferred  from 
the  dismounted  fork  to  the  mounted  one. 

That  the  motion  should  thus  transfer  itself  through  the 
air  it  is  necessary  that  the  two  forks  should  be  in  perfect 
unison.  If  a  morsel  of  wax  not  larger  than  a  pea  be  placed 
on  one  of  the  forks,  it  is  rendered  thereby  powerless 
io  affect,  or  to  be  affected  by,  the  other.  It  is  easy  to 
understand  this  experiment.  The  pulses  of  the  one  fork 
can  affect  the  other,  because  they  are  perfectly  timed.  A 
single  pulse  causes  the  prong  of  the  silent  fork  to  vibrate 
through  an  infinitesimal  space.  But  just  as  it  has  com- 
pleted this  small  vibration,  another  pulse  is  ready  to  strike 
it.  Thus,  the  impulses  add  themselves  together.  In 
the  five  seconds  during  which  the  forks  were  held  near 
each  other,  the  vibrating  fork  sent  1,280  waves  against 
its  neighbour,  and  those  1,280  shocks,  all  delivered  at  the 
proper  moment,  all,  as  I  have  said,  perfectly  timed,  have 
given  such  strength  to  the  vibrations  of  the  mounted  fork 
as  to  render  them  audible  to  all. 

Another  curious  illustration  of  the  influence  of  syn- 


RADIANT   HEAT  AND    ITS   RELATIONS.  79 

chronism  on  musical  vibrations,  is  this  :  Three  small  gas- 
flames  are  inserted  into  three  glass  tubes  of  different 
lengths.  Each  of  these  flames  can  be  caused  to  emit 
a  musical  note,  the  pitch  of  which  is  determined  by 
the  length  of  the  tube  surrounding  the  flame.  The 
shorter  the  tube  the  higher  is  the  pitch.  The  flames  are 
now  silent  within  their  respective  tubes,  but  each  of 
them  can  be  caused  to  respond  to  a  proper  note  sounded 
anywhere  in  this  room.  With  an  instrument  called  a  syren, 
a  powerful  musical  note,  of  increasing  pitch,  can  be  pro- 
duced. Beginning  with  a.  note  of  low  pitch,  and  ascending 
gradually  to  a  higher  one,  we  finally  attain  the  note  of  the 
flame  in  the  longest  tube.  The  moment  it  is  reached, 
the  flame  bursts  into  song.  The  other  flames  are  still 
silent  within  their  tubes.  But  by  urging  the  instrument 
on  to  higher  notes,  the  second  flame  is  started,  and  the 
third  alone  remains.  A  still  higher  note  starts  it  also. 
Thus,  as  the  sound  of  the  syren  rises  gradually  in  pitch, 
it  awakens  every  flame  in  passing,  by  striking  it  with 
a  series  of  waves  whose  periods  of  recurrence  are  similar 
to  its  own. 

Now  the  wave-motion  from  the  syren  is  in  part  taken 
up  by  the  flame  which  synchronises  with  the  waves ;  and 
had  these  waves  to  impinge  upon  a  multitude  of  flames, 
instead  of  upon  one  flame  only,  the  transference  might  be 
so  great  as  to  absorb  the  whole  of  the  original  wave-motion. 
Let  us  apply  these  facts  to  radiant  heat.  This  blue  flame 
is  the  flame  of  carbonic  oxide ;  this  transparent  gas  is 
carbonic  acid  gas.  In  the  blue  flame  we  have  carbonic 
acid  intensely  heated,  or,  in  other  words,  in  a  state  of 
intense  vibration.  It  thus  resembles  the  sounding  fork, 
while  this  cold  carbonic  acid  resembles  the  silent  one. 
What  is  the  consequence  ?  Through  the  synchronism  of 
the  hot  and  cold  gas,  transmission  of  the  radiant  heat  of 
the  former  through  the  latter  is  prevented.  The  cold  gas 


80  FRAGMENTS   OF   SCIENCE. 

is  intensely  opaque  to  the  radiation  from  this  par- 
ticular flame,  though  highly  transparent  to  heat  of  every 
other  kind.  We  are  here  manifestly  dealing  with 
that  great  principle  which  lies  at  the  basis  of  spectrum 
analysis,  and  which  has  enabled  scientific  men  to  deter- 
mine the  substances  of  which  the  sun,  the  stars,  and  even 
the  nebulae  are  composed :  the  principle,  namely,  that  a 
body  which  is  competent  to  emit  any  ray,  whether  of  heat 
or  light,  is  competent  in  the  same  degree  to  absorb  that 
ray.  The  absorption  depends  on  the  synchronism  exist- 
ing between  the  vibrations  of  the  atoms  from  which  the 
rays,  or  more  correctly  the  ivaves,  issue,  and  those  of  the 
atoms  on  which  they  impinge. 

To  its  incompetence  to  emit  white  light,  aqueous 
vapour  adds  incompetence  to  absorb  white  light.  It  can~ 
not,  for  example,  absorb  the  luminous  rays  of  the  sun, 
though  it  can  absorb  the  non-luminous  rays  of  the  earth. 
This  incompetence  of  the  vapour  to  absorb  luminous  rays 
is  shared  by  water  and  ice — in  fact,  by  all  really  trans- 
parent substances.  Their  transparency  is  due  to  their 
inability  to  absorb  luminous  rays.  The  molecules  of  such 
substances  are  in  dissonance  with  the  luminous  waves; 
and  hence  such  waves  pass  through  transparent  bodies 
without  disturbing  the  molecular  rest.  A  purely  luminous 
beam,  however  intense  may  be  its  heat,  is  sensibly  incom- 
petent to  melt  the  smallest  particle  of  ice.  We  can,  for 
example,  converge  a  powerful  luminous  beam  upon  a  sur- 
face covered  with  hoar  frost,  with  out  melting  a  single  spicula 
of  the  ice  crystals.  How  then,  it  may  be  asked,  are  the 
snows  of  the  Alps  swept  away  by  the  sunshine  of  summer  ? 
I  answer,  they  are  not  swept  away  by  sunshine  at  all,  but 
by  rays  which  have  no  sunshine  whatever  in  them.  The 
luminous  rays  of  the  sun  fall  upon  the  snow-fields  and 
are  flashed  in  echoes  from  crystal  to  crystal,  but  they  find 
next  to  no  lodgment  within  the  crystals.  They  are  hardly 


RADIANT   HEAT   AND   ITS   RELATIONS.  81 

at  all  absorbed,  and  hence  they  cannot  produce  fusion. 
But  a  body  of  powerful  dark  rays  is  emitted  by  the  sun ; 
and  it  is  these  that  cause  the  glaciers  to  shrink  and 
the  snows  to  disappear  ;  it  is  they  that  fill  the  banks  of 
the  Arve  and  Arveyron,  and  liberate  from  their  frozen 
captivity  the  Rhone  and  the  Rhine. 

Placing  a  concave  silvered  mirror  behind  the  electric 
light  its  rays  are  converged  to  a  focus  of  dazzling  bril- 
liancy. Placing  in  the  path  of  the  rays,  between  the  light 
and  the  focus,  a  vessel  of  water,  and  introducing  at  the 
focus  a  piece  of  ice,  the  ice  is  not  melted  by  the  concen- 
trated beam.  Matches,  at  the  same  place,  are  ignited, 
and  wood  is  set  on  fire.  The  powerful  heat,  then,  of 
this  luminous  beam  is  incompetent  to  melt  the  ice.  On 
withdrawing  the  cell  of  water,  the  ice  immediately 
liquefies,  and  the  water  trickles  from  it  in  drops.  Re- 
introducing  the  cell  of  water,  the  fusion  is  arrested, 
and  the  drops  cease  to  fall.  The  transparent  water  of 
the  cell  exerts  no  sensible  absorption  on  the  luminous 
rays,  still  it  withdraws  something  from  the  beam,  which, 
when  permitted  to  act,  is  competent  to  melt  the  ice. 
This  something  is  the  dark  radiation  of  the  electric 
light.  Again,  I  place  a  slab  of  pure  ice  in  front  of  the 
electric  lamp ;  send  a  luminous  beam  first  through  our 
cell  of  water  and  then  through  the  ice.  By  means  of 
a  lens  an  image  of  the  slab  is  cast  upon  a  white  screen. 
The  beam,  sifted  by  the  water,  has  little  power  upon  the 
ice.  But  observe  what  occurs  when  the  water  is  removed; 
we  have  here  a  star  and  there  a  star,  each  star  resembling 
a  flower  of  six  petals,  and  growing  visibly  larger  before 
our  eyes.  As  the  leaves  enlarge,  their  edges  become  ser- 
rated, but  there  is  no  deviation  from  the  six-rayed  type. 
We  have  here,  in  fact,  the  crystallisation  of  the  ice  inverted 
by  the  invisible  rays  of  the  electric  beam.  They  take  the 
molecules  down  in  this  wonderful  way,  and  reveal  to  us 


82  FRAGMENTS   OF   SCIENCE. 

the  exquisite  atomic  structure  of  the  substance  with  which 
Nature  every  winter  roofs  our  ponds  and  lakes. 

Numberless  effects,  apparently  anomalous,  might  be 
adduced  in  illustration  of  the  action  of  these  lightless  rays. 
These  two  powders,  for  example,  are  both  white,  and 
undistinguishable  from  each  other  by  the  eye.  The 
luminous  rays  of  the  sun  are  unabsorbed  by  both — from 
such  rays  these  powders  acquire  no  heat ;  still  one  of 
them,  sugar,  is  heated  so  highly  by  the  concentrated 
beam  of  the  electric  lamp,  that  it  first  smokes  and  then 
violently  inflames,  while  the  other  substance,  salt,  is 
barely  warmed  at  the  focus.  Placing  two  perfectly 
transparent  liquids  in  test-tubes  at  the  focus,  one  of 
them  boils  in  a  couple  of  seconds,  while  the  other,  in  a 
similar  position,  is  hardly  warmed.  The  boiling-point 
of  the  first  liquid  is  78°  C.,  which  is  speedily  reached ; 
that  of  the  second  liquid  is  only  48°  C.,  which  is  never 
reached  at  all.  These  anomalies  are  entirely  due  to  the 
unseen  element  which  mingles  with  the  luminous  rays  of 
the  electric  beam,  and  indeed  constitutes  90  per  cent,  of 
its  calorific  power. 

A  substance,  as  many  of  you  know,  has  been  discovered, 
by  which  these  dark  rays  may  be  detached  from  the  total 
emission  of  the  electric  lamp.  This  ray-filter  is  a  liquid, 
black  as  pitch  to  the  luminous,  but  bright  as  a  diamond 
to  the  non-luminous,  radiation.  It  mercilessly  cuts  off  the 
former,  but  allows  the  latter  free  transmission.  When 
these  invisible  rays  are  brought  to  a  focus,  at  a  distance 
of  several  feet  from  the  electric  lamp,  the  dark  rays  form 
an  invisible  image  of  their  source.  By  proper  means, 
this  image  may  be  transformed  into  a  visible  one  of 
dazzling  brightness.  It  might,  moreover,  be  shown,  if 
time  permitted,  how,  out  of  those  perfectly  dark  rays, 
could  be  extracted,  by  a  process  of  transmutation,  all  the 
colours  of  the  solar  spectrum.  It  might  also  be  proved 


RADIANT   HEAT  AND   ITS  RELATIONS.  83 

that  those  rays,  powerful  as  they  are,  and  sufficient  to 
fuse  many  metals,  can  be  permitted  to  enter  the  eye,  and 
to  break  upon  the  retina,  without  producing  the  least 
luminous  impression. 

The  dark  rays  being  thus  collected,  you  see  nothing 
at  their  place  of  convergence.  With  a  proper  thermo- 
meter it  could  be  proved  that  even  the  air  at  the  focus 
is  just  as  cold  as  the  surrounding  air.  And  mark  the 
conclusion  to  which  this  leads.  It  proves  the  aether  at 
the  focus  to  be  practically  detached  from  the  air, — that 
the  most  violent  aethereal  motion  may  there  exist,  without 
the  least  aerial  motion.  But,  though  you  see  it  not,  there 
is  sufficient  heat  at  that  focus  to  set  London  on  fire. 
The  heat  there  is  competent  to  raise  iron  to  a  temper- 
ature at  which  it  throws  off  brilliant  scintillations.  It 
can  heat  platinum  to  whiteness,  and  almost  fuse  that  re- 
fractory metal.  It  actually  can  fuse  gold,  silver,  copper, 
and  aluminium.  The  moment,  moreover,  that  wood  is 
placed  at  the  focus  it  bursts  into  a  blaze. 

It  has  been  already  affirmed  that,  whether  as  regards 
radiation  or  absorption,  the  elementary  atoms  possess  but 
little  power.  This  might  be  illustrated  by  a  long  array 
of  facts  ;  and  one  of  the  most  singular  of  these  is  furnished 
by  the  deportment  of  that  extremely  combustible  substance, 
phosphorus,  when  placed  at  the  dark  focus.  It  is  impos- 
sible to  ignite  there  a  fragment  of  amorphous  phosphorus. 
But  ordinary  phosphorus  is  a  far  quicker  combustible,  and 
its  deportment  towards  radiant  heat  is  still  more  impressive. 
It  may  be  exposed  to  the  intense  radiation  of  an  ordinary 
fire  without  bursting  into  flame.  It  may  also  be  exposed  for 
twenty  or  thirty  seconds  at  an  obscure  focus,  of  sufficient 
power  to  raise  platinum  to  a  red  heat,  without  ignition. 
Notwithstanding  the  energy  of  the  aethereal  waves  here 
concentrated,  notwithstanding  the  extremely  inflammable 
character  of  the  elementary  body  exposed  to  their  action, 


84  FRAGMENTS  OF   SCIENCE. 

the  atoms  of  that  body  refuse  to  partake  of  the  motion  of 
the  powerful  waves  of  low  refrangibility,  and  consequently 
cannot  be  affected  by  their  heat. 

The  knowledge  we  now  possess  will  enable  us  to 
analyse  with  profit  a  practical  question.  White  dresses 
are  worn  in  summer,  because  they  are  found  to  be 
cooler  than  dark  ones.  The  celebrated  Benjamin  Franklin 
placed  bits  of  cloth  of  various  colours  upon  snow,  exposed 
them  to  direct  sunshine,  and  found  that  they  sank  to 
different  depths  in  the  snow.  The  black  cloth  sank  deepest, 
the  white  did  not  sink  at  all.  Franklin  inferred  from  this 
experiment  that  black  bodies  are  the  best  absorbers,  and 
white  ones  the  worst  absorbers,  of  radiant  heat.  Let 
us  test  the  generality  of  this  conclusion.  One  of  these 
two  cards  is  coated  with  a  very  dark  powder,  and  the 
other  with  a  perfectly'  white  one.  I  place  the  pow- 
dered surfaces  before  a  fire,  and  leave  them  there 
until  they  have  acquired  as  high  a  temperature  as  they 
can  attain  in  this  position.  Which  of  the  cards  is  then 
most  highly  heated  ?  It  requires  no  thermometer  to  answer 
this  question  ?  Simply  pressing  the  back  of  the  card,  on 
which  the  white  powder  is  strewn,  against  the  cheek  or 
forehead,  it  is  found  intolerably  hot.  Placing  the  dark  card 
in  the  same  position,  it  is  found  cool.  The  white  powder  has 
absorbed  far  more  heat  than  the  dark  one.  This  simple 
result  abolishes  a  hundred  conclusions  which  have  been 
hastily  drawn  from  the  experiment  of  Franklin.  Again, 
here  are  suspended  two  delicate  mercurial  thermometers 
at  the  same  distance  from  a  gas-flame.  The  bulb  of  one 
of  them  is  covered  by  a  dark  substance,  the  bulb  of  the 
other  by  a  white  one.  Both  bulbs  have  received  the  radia- 
tion from  the  flame,  but  the  white  bulb  has  absorbed  most, 
and  its  mercury  stands  much  higher  than  that  of  the  other 
thermometer.  This  experiment  might  be  varied  in  a 
hundred  ways :  it  proves  that  from  the  darkness  of  a 


RADIANT  HEAT  AND   ITS  RELATIONS.  85 

body  you  can  draw  no  certain  conclusion  regarding  its 
power  of  absorption. 

The  reason  of  this  simply  is,  that  colour  gives  us  intel- 
ligence of  only  one  portion,  and  that  the  smallest  one,  of 
the  rays  impinging  on  the  coloured  body.  Were  the 
rays  all  luminous,  we  might  with  certainty  infer  from  the 
colour  of  a  body  its  power  of  absorption ;  but  the  great 
mass  of  the  radiation  from  our  fire,  our  gas-flame,  and 
even  from  the  sun  itself,  consists  of  invisible  calorific  rays, 
regarding  which  colour  teaches  us  nothing.  A  body  may 
be  highly  transparent  to  the  one  class  of  rays,  and  highly 
opaque  to  the  other.  Thus  the  white  powder,  which 
has  shown  itself  so  powerful  an  absorber,  has  been 
specially  selected  on  account  of  its  extreme  perviousness 
to  the  visible  rays,  and  its  extreme  imperviousness  to  the 
invisible  ones  ;  while  the  dark  powder  was  chosen  on  ac- 
count of  its  extreme  transparency  to  the  invisible,  and  its 
extreme  opacity  to  the  visible,  rays.  In  the  case  of  fhe 
radiation  from  our  fire,  about  9  8  per  cent,  of  the  whole  emis- 
sion consists  of  invisible  rays  ;  the  body,  therefore,  which 
was  most  opaque  to  these  triumphed  as  an  absorber, 
though  that  body  was  a  white  one. 

And  here  it  is  worth  while  to  consider  the  manner  in 
which  we  obtain  from  natural  facts  what  may  be  called 
their  intellectual  value.  Throughout  the  processes  of 
Nature  we  have  interdependence  and  harmony ;  and  the 
main  value  of  physics,  considered  as  a  mental  dis- 
cipline, consists  in  the  tracing  out  of  this  interdependence, 
and  the  demonstration  of  this  harmony.  The  outward 
and  visible  phenomena  are  the  counters  of  the  intel- 
lect ;  and  our  science  would  not  be  worthy  of  its  name 
and  fame  if  it  halted  at  facts,  however  practically  useful, 
and  neglected  the  laws  which  accompany  and  rule  the 
phenomena.  Let  us  endeavour,  then,  to  extract  from  the 
experiment  of  Franklin  all  that  it  can  yield,  calling 


86  FEAGMENTS   OF  SCIENCE. 

to  our  aid  the  knowledge  which  our  predecessors  have 
already  stored.  Let  us  imagine  two  pieces  of  cloth  of 
the  same  texture,  the  one  black  and  the  other  white, 
placed  upon  sunned  snow.  Fixing  our  attention  on  the 
white  piece,  let  us  enquire  whether  there  is  any  reason 
to  expect  that  it  will  sink  in  the  snow  at  all.  There  is 
knowledge  at  hand  which  enables  us  to  reply  at  once  in 
the  negative.  There  is,  on  the  contrary,  reason  to  expect 
that,  after  a  sufficient  exposure,  the  bit  of  cloth  will  be 
found  on  an  eminence  instead  of  in  a  hollow ;  that  in- 
stead of  a  depression,  we  shall  have  a  relative  elevation 
of  the  bit  of  cloth.  For,  as  regards  the  luminous  rays  of 
the  sun,  the  cloth  and  the  snow  are  alike  powerless  ;  the 
one  cannot  be  warmed,  nor  the  other  melted,  by  such 
rays.  The  cloth  is  white  and  the  snow  is  white,  because 
their  confusedly  mingled  fibres  and  particles  are  incom- 
petent to  absorb  the  luminous  rays.  Whether,  then,  the 
cloth  will  sink  or  not  depends  entirely  upon  the  dark 
rays  of  the  sun.  Now  the  substance  which  absorbs  these 
dark  rays  with  the  greatest  avidity  is  ice, — or  snow, 
which  is  merely  ice  in  powder.  Hence,  a  less  amount  of 
heat  will  be  lodged  in  the  cloth  than  in  the  surrounding 
snow.  The  cloth  must  therefore  act  as  a  shield  to  the 
snow  on  which  it  rests  ;  and,  in  consequence  of  the  more 
rapid  fusion  of  the  exposed  snow,  its  shield  must,  in  due 
time,  be  left  behind,  perched  upon  an  eminence  like  a 
glacier-table. 

But  though  the  snow  transcends  the  cloth,  both  as  a 
radiator  and  absorber,  it  does  not  much  transcend  it. 
Cloth  is  very  powerful  in  both  these  respects.  Let  us 
now  turn  our  attention  to  the  piece  of  black  cloth,  the 
texture  and  fabric  of  which  I  assume  to  be  the  same  as 
that  of  the  white.  For  our  object  being  to  compare  the 
effects  of  colour,  we  must,  in  order  to  study  this  effect  in  its 


RADIANT   HEAT   AND   ITS   RELATIONS.  87 

purity,  preserve  all  the  other  conditions  constant.  Let  us 
then  suppose  the  black  cloth  to  be  obtained  from  the  dye- 
ing of  the  white.  The  cloth  itself,  without  reference  to 
the  dye,  is  nearly  as  good  an  absorber  of  heat  as  the  snow 
around  it.  But  to  the  absorption  of  the  dark  solar  rays 
by  the  undyed  cloth,  is  now  added  the  absorption  of  the 
whole  of  the  luminous  rays,  and  this  great  additional  in- 
flux of  heat  is  far  more  than  sufficient  to  turn  the  balance 
in  favour  of  the  black  cloth.  The  sum  of  its  actions  on  the 
dark  and  luminous  rays,  exceeds  the  action  of  the  snow  on 
the  dark  rays  alone.  Hence  the  cloth  will  sink  in  the  snow, 
and  this  is  the  complete  analysis  of  Franklin's  experiment. 

Throughout  this  discourse  the  main  stress  has  been 
laid  on  chemical  constitution,  as  influencing  most  power- 
fully the  phenomena  of  radiation  and  absorption.  With 
regard  to  gases  and  vapours,  and  to  the  liquids  from  which 
these  vapours  are  derived,  it  has  been  proved  by  the  most 
varied  and  conclusive  experiments  that  the  acts  of  radia- 
tion and  absorption  are  molecular — that  they  depend  upon 
chemical,  and  not  upon  mechanical,  condition.  In  at- 
tempting to  extend  this  principle  to  solids  I  was  met  by  a 
multitude  of  facts,  obtained  by  celebrated  experimenters, 
which  seemed  flatly  to  forbid  such  an  extension.  Melloni, 
for  example,  had  found  the  same  radiant  and  absorbent 
power  for  chalk  and  lamp-black.  MM.  Masson  and  Cour- 
tepee  had  performed  a  most  elaborate  series  of  experiments 
on  chemical  precipitates  of  various  kinds,  and  found  that 
they  one  and  all  manifested  the  same  power  of  radiation. 
They  concluded  from  their  researches,  that  when  bodies 
are  reduced  to  an  extremely  fine  state  of  division,  the 
influence  of  this  state  is  so  powerful  as  entirely  to  mask 
and  override  whatever  influence  may  be  due  to  chemical 
constitution. 

But  it  appears  to  me  that  through  the  whole  of  these 


88  FRAGMENTS   OF  SCIENCE. 

researches  an  oversight  has  run,  the  mere  mention  of  which 
will  show  what  caution  is  essential  in  the  operations  of 
experimental  philosophy ;  while  an  experiment  or  two 
will  make  clear  wherein  the  oversight  consists.  Filling 
a  brightly  polished  metal  cube  with  boiling  water,  I 
determine  the  quantity  of  heat  emitted  by  two  of  the 
bright  surfaces.  As  a  radiator  of  heat  one  of  them 
far  transcends  the  other.  Both  surfaces  appear  to  be 
metallic ;  what,  then,  is  the  cause  of  the  observed  differ- 
ence in  their  radiative  power  ?  Simply  this  :  one  of  the 
surfaces  is  coated  with  transparent  gum,  through  which, 
of  course,  is  seen  the  metallic  lustre  behind ;  and  this 
varnish,  though  so  perfectly  transparent  to  luminous 
rays,  is  as  opaque  as  pitch,  or  lamp-black,  to  non-lumi- 
nous ones.  It  is  a  powerful  emitter  of  dark  rays;  it 
is  also  a  powerful  absorber.  While,  therefore,  at  the 
present  moment,  it  is  copiously  pouring  forth  radiant 
heat  itself,  it  does  not  allow  a  single  ray  from  the  metal 
behind  to  pass  through  it.  The  varnish  then,  and  not 
the  metal,  is  the  real  radiator. 

Now  Melloni,  and  Masson,  and  Courtepee  experimented 
thus :  they  mixed  •  their  powders  and  precipitates  with 
gum-water,  and  laid  them,  by  means  of  a  brush,  upon  the 
surfaces  of  a  cube  like  this.  True,  they  saw  their  red 
powders  red,  their  white  ones  white,  and  their  black  ones 
black,  but  they  saw  these  colours  through  the  coat  of 
varnish  which  encircled  every  particle  of  their  powders. 
When,  therefore,  it  was  concluded  that  colour  had  no 
influence  on  radiation,  no  chance  had  been  given  to  it  of 
asserting  its  influence  ;  when  it  was  found  that  all  chemi- 
cal precipitates  radiated  alike,  it  was  the  radiation  from  a 
varnish,  common  to  them  all,  which  showed  the  observed 
constancy.  Hundreds,  perhaps  thousands,  of  experiments 
on  radiant  heat  have  been  performed  in  this  way,  by 
various  enquirers,  but  the  work  will,  I  fear,  have  to  be 


RADIANT   HEAT    AND    ITS   RELATIONS.  89 

done  over  again.  I  am  not,  indeed,  acquainted  with  an 
instance  in  which  an  oversight  of  so  trivial  a  character 
has  been  committed  by  so  many  able  men  in  succession, 
and  vitiated  so  large  an  amount  of  otherwise  excellent 
work. 

Basing  our  reasonings  thus  on  demonstrated  facts,  we 
arrive  at  the  extremely  probable  conclusion  that  the  en- 
velope of  the  particles,  and  not  the  particles  themselves, 
was  the  real  radiator  in  the  experiments  just  referred  to. 
To  reason  thus,  and  deduce  their  more  or  less  probable 
consequences  from  experimental  facts,  is  an  incessant 
exercise  of  the  student  of  physical  science.  But  having 
thus  followed,  for  a  time,  the  light  of  reason  alone  through 
a  series  of  phenomena,  and  emerged  from  them  with  a 
purely  intellectual  conclusion,  our  duty  is  to  bring  that 
conclusion  to  an  experimental  test.  In  this  way  we  fortify 
our  science,  sparing  no  pains  and  shirking  no  toil,  to  secure 
sound  materials  for  the  edifice  which  it  is  our  privilege 
to  raise. 

For  the  purpose  of  testing  our  conclusion  regarding  the 
influence  of  the  gum,  I  take  two  powders  presenting  the 
same  physical  appearance  ;  one  of  them  is  a  compound  of 
mercury,  and  the  other  a  compound  of  lead.  On  two  sur- 
faces of  a  cube  are  spread  these  bright  red  powders,  with- 
out varnish  of  any  kind.  Filling  the  cube  with  boiling 
water,  and  determining  the  radiation  from  the  two  surfaces, 
one  of  them  is  found  to  emit  thirty-nine  units  of  heat,  while 
the  other  emits  seventy-four.  This,  surely,  is  a  great  dif- 
ference. Here,  however,  is  a  second  cube,  having  two  of 
its  surfaces  coated  with  the  same  powders,  the  only  dif- 
ference being  that  the  powders  are  laid  on  by  means  of 
a  transparent  gum.  Both  surfaces  are  now  absolutely 
alike  in  radiative  power.  Both  of  them  emit  somewhat 
more  than  was  emitted  by  either  of  the  unvarnished  powders, 
simply  because  the  gum  employed  is  a  better  radiator  than 


90  FRAGMENTS   OP  SCIENCE. 

either  of  them.  Excluding  all  varnish,  and  comparing 
white  -with  white,  vast  differences  are  found ;  comparing 
black  with  black,  they  are  also  different;  and  when 
black  and  white  are  compared,  in  some  cases  the  black 
radiates  far  more  than  the  white,  while  in  other  cases  the 
white  radiates  far  more  than  the  black.  Determining, 
moreover,  the  absorptive  power  of  those  powders,  it  is 
found  to  go  hand-in-hand  with  their  radiative  power. 
The  good  radiator  is  a  good  absorber,  and  the  bad  radiator 
is  a  bad  absorber.  From  all  this  it  is  evident  that  as  re- 
gards the  radiation  and  absorption  of  non-luminous  heat, 
colour  teaches  us  nothing ;  and  that  even  as  regards  the 
radiation  of  the  sun,  consisting  as  it  does  mainly  of  non- 
luminous  rays,  conclusions  as  to  the  influence  of  colour 
may  be  altogether  delusive.  This  is  the  strict  scientific 
upshot  of  our  researches.  But  it  is  not  the  less  true  that 
in  the  case  of  wearing  apparel — and  this  for  reasons  which 
I  have  given  in  analysing  the  experiment  of  Franklin — 
black  dresses  are  more  potent  than  white  ones  as  absorbers 
of  solar  heat. 

Thus,  in  brief  outline,  have  been  brought  before  you  a 
few  of  the  results  of  recent  enquiry.  If  you  ask  me  what 
is  the  use  of  them,  I  can  hardly  answer  you,  unless  you 
define  the  term  use.  If  you  meant  to  ask  whether 
those  dark  rays  which  clear  away  the  Alpine  snows,  will 
ever  be  applied  to  the  roasting  of  turkeys,  or  the  driving 
of  steam-engines — while  affirming  their  power  to  do  both, 
I  would  frankly  confess  that  they  are  not  at  present 
capable  of  competing  profitably  with  coal  in  these  parti- 
culars. Still  they  may  have  great  uses  unknown  to  me  ; 
and  when  our  coal-fields  are  exhausted,  it  is  possible  that 
a  more  aethereal  race  than  we  are  may  cook  their 
victuals,  and  perform  their  work,  in  this  transcendental 
way.  But  is  it  necessary  that  the  student  of  science 
should  have  his  labours  tested  by  their  possible  practical 


RADIANT   HEAT   AND    ITS   RELATIONS.  91 

applications  ?  What  is  the  practical  value  of  Homer's 
Iliad  ?  You  smile,  and  possibly  think  that  Homer's  Iliad 
is  good  as  a  means  of  culture.  There's  the  rub.  The 
people  who  demand  of  science  practical  uses,  forget,  or  do 
not  know,  that  it  also  is  great  as  a  means  of  culture — that 
the  knowledge  of  this  wonderful  universe  is  a  thing  profit- 
able in  itself,  and  requiring  no  practical  application  to  jus- 
tify its  pursuit. 

But  while  the  student  of  Nature  distinctly  refuses 
to  have  his  labours  judged  by  their  practical  issues,  un- 
less the  term  practical  be  made  to  include  mental  as 
well  as  material  good,  he  knows  full  well  that  the  greatest 
practical  triumphs  have  been  episodes  in  the  search  after 
pure  natural  truth.  The  electric  telegraph  is  the  standing 
wonder  of  this  age,  and  the  men  whose  scientific  know- 
ledge, and  mechanical  skill,  have  made  the  telegraph  what 
it  is,  are  deserving  of  all  honour.  In  fact,  they  have  had 
their  reward,  both  in  reputation  and  in  those  more  substan- 
tial benefits  which  the  direct  service  of  the  public  always 
carries  in  its  train.  But  who,  I  would  ask,  put  the  soul 
into  this  telegraphic  body  ?  Who  snatched  from  heaven 
the  fire  that  flashes  along  the  line  ?  This,  I  am  bound  to 
say,  was  done  by  two  men,  the  one  a  dweller  in  Italy,1 
the  other  a  dweller  in  England,2  who  never  in  their 
enquiries  consciously  set  a  practical  object  before  them, 
— whose  only  stimulus  was  the  fascination  which  draws 
the  climber  to  a  never-trodden  peak,  and  would  have 
made  Caesar  quit  his  victories  for  the  sources  of  the 
Nile.  That  the  knowledge  brought  us  by  those  prophets, 
priests,  and  kings  of  science  is  what  the  world  calls 
useful  knowledge,  the  triumphant  application  of  their 
discoveries  proves.  But  science  has  another  function 
to  fulfil,  in  the  storing  and  the  training  of  the  human 

'  Volta.  *  Faraday. 


FEAGMENTS   OF   SCIENCE. 


mind ;  and  I  would  base  my  appeal  to  you  on  the 
specimen  which  has  this  evening  been  brought  before  you, 
whether  any  system  of  education  at  the  present  day  can 
be  deemed  even  approximately  complete,  in  which  the 
knowledge  of  Nature  is  neglected  or  ignored. 


The  opening  paragraph  of  this  article,  as  indeed  many 
others  in  this  volume,  show  that  'the  crossing  of  the 
boundary  of  experiment,'  the  mention  of  which  caused  so 
much  commotion  last  year,  is  no  new  heresy  of  mine. 
December  1875. 


Ca/, 


rv. 

NEW  CHEMICAL  REACTIONS  PRODUCED  BY  LIGHT. 


§   I- 

IN  1868  I  asked  permission  of  theKoyal  Society  to  draw 
the  attention  of  chemists  to  a  method  of  experiment 
which,  though  simple,  was  unknown.  It  consists  in  sub- 
jecting the  vapours  of  volatile  liquids  to  the  action  of 
concentrated  sunlight,  or  to  the  concentrated  beam  of 
the  electric  light.  This  communication  was  the  imme- 
diate antecedent  of  the  discourse  on  '  Dust  and  Disease ' 
which  follows  it  in  this  volume ;  and  as  such  is  introduced 
here. 

Action  of  the  Electric  Light. 

A  glass  tube  2'8  feet  long  and  of  2'5  inches  internal 
diameter,  which  had  been  frequently  employed  in  my  re- 
searches on  radiant  heat,  was  supported  horizontally.  At 
one  end  of  it  was  placed  an  electric  lamp,  the  height  and 
position  of  both  being  so  arranged,  that  the  axis  of  the 
glass  tube,  and  that  of  the  parallel  beam  issuing  from 
the  lamp,  were  coincident.  The  tube  in  the  first  experi- 
ments was  closed  by  plates  of  rock-salt,  and  subsequently 
by  plates  of  glass. 

This  tube  which,  as  on  former  occasions,  for  the  sake 
of  distinction,  I  call  the  experimental  tube,  was  connected 
with  an  air-pump,  and  also  with  a  series  of  drying  and 
other  tubes  used  for  the  purification  of  the  air. 


04  FRAGMENTS   OP   SCIENCE. 

A  number  of  test-tubes,  like  F,  fig.  2  (I  have  used  at 
least  fifty  of  them),  were  converted  into  Woulfs  flasks. 
FIG.  2.  Each  of  them  was  stopped  by  a 

cork,  through  which  passed  two 
glass  tubes :  one  of  these  tubes 
(a)  ended  immediately  below  the 
cork,  while  the  other  (6)  descended 
to  the  bottom  of  the  flask,  being 
drawn  out  at  its  lower  end  to  an 
orifice  about  0'03  of  an  inch  in 
diameter.  It  was  found  necessary 
to  coat  the  cork  carefully  with 
cement. 

The  little  flask,  thus  formed, 
was  partially  filled  with  the  liquid 
whose  vapour  was  to  be  examined; 
it  was  then  introduced  into  the 
path  of  the  purified  current  of  air. 
The  experimental  tube  being 
exhausted,  and  the  cock  which  cut 
off  the  supply  of  purified  air  being 
cautiously  turned  on,  the  air  en- 
tered the  flask  through  the  tube 
6,  and  escaped  by  the  small  orifice 
at  the  lower  end  of  fc  into  the  liquid.  Through  this  it 
bubbled,  loading  itself  with  vapour,  after  which  the  mixed 
air  and  vapour,  passing  from  the  flask  by  the  tube  a, 
entered  the  experimental  tube,  where  they  were  subjected 
to  the  action  of  light. 

The  power  of  the  electric  beam  to  reveal  the  existence 
of  anything  within  the  experimental  tube,  or  the  im- 
purities of  the  tube  itself,  is  extraordinary.  When  the 
experiment  is  made  in  a  darkened  room,  a  tube  which  in 
ordinary  daylight  appears  absolutely  clean,  is  often  shown 
by  the  present  mode  of  examination  to  be  exceedingly  filthy. 


DECOMPOSITION  BY  LIGHT.  95 

The  following  are  some  of  the  results  obtained  with 
this  arrangement : — 

Nitrite  of  amyl. — The  vapour  of  this  liquid  was  in 
the  first  instance  permitted  to  enter  the  experimental  tube, 
while  the  beam  from  the  electric  lamp  was  passing  through 
it.  Curious  clouds  were  observed  to  form  near  the  place 
of  entry,  which  were  afterwards  whirled  through  the 
tube. 

The  tube  being  again  exhausted,  the  mixed  air  and 
vapour  were  allowed  to  enter  it  in  the  dark.  The  slightly 
convergent  beam  of  the  electric  light  was  then  sent 
through  the  tube,  from  end  to  end.  For  a  moment  the 
tube  was  optically  empty,  nothing  whatever  was  seen 
within  it;  but  before  a  second  had  elapsed  a  shower  of 
liquid  spherules  was  precipitated  on  the  beam,  thus  gene- 
rating a  cloud  within  the  tube.  This  cloud  became  denser 
as  the  light  continued  to  act,  showing  at  some  places  vivid 
iridescence. 

The  beam  of  the  electric  lamp  was  now  converged  so 
as  to  form  within  the  tube  a  cone  of  rays  about  eight 
inches  long.  The  tube  was  cleansed  and  again  filled 
in  darkness.  When  the  light  was  sent  through  it,  the 
precipitation  upon  the  beam  was  so  rapid  and  intense 
that  the  cone,  which  a  moment  before  was  invisible, 
flashed  suddenly  forth  like  a  solid  luminous  spear. 

The  effect  was  the  same  when  the  air  and  vapour  were 
allowed  to  enter  the  tube  in  diffuse  daylight.  The  cloud, 
however,  which  shone  with  such  extraordinary  radiance 
under  the  electric  beam,  was  invisible  in  the  ordinary 
light  of  the  laboratory. 

The  quantity  of  mixed  air  and  vapour  within  the  ex- 
perimental tube  could  of  course  be  regulated  at  pleasure. 
The  rapidity  of  the  action  diminished  with  the  attenuation 
of  the  vapour.  When,  for  example,  the  mercurial  column 
associated  with  the  experimental  tube  was  depressed  onty 


96  FRAGMENTS  OP  SCIENCE. 

five  inches,  the  action  was  not  nearly  so  rapid  as  when  the 
tube  was  full.  In  such  cases,  however,  it  was  exceedingly 
interesting  to  observe,  after  some  seconds  of  waiting,  a 
thin  streamer  of  delicate  bluish-white  cloud  slowly  form- 
ing along  the  axis  of  the  tube,  and  finally  swelling  so  as 
to  fill  it. 

When  dry  oxygen  was  employed  to  carry  in  the  vapour, 
the  effect  was  the  same  as  that  obtained  with  air. 

When  dry  hydrogen  was  used  as  a  vehicle,  the  effect 
was  also  the  same. 

The  effect,  therefore,  is  not  due  to  any  interaction 
between  the  vapour  of  the  nitrite  and  its  vehicle. 

This  was  further  demonstrated  by  the  deportment  of 
the  vapour  itself.  When  it  was  permitted  to  enter  the 
experimental  tube  unmixed  with  air  or  any  other  gas,  the 
effect  was  substantially  the  same.  Hence  the  seat  of  the 
observed  action  is  the  vapour. 

This  action  is  not  to  be  ascribed  to  heat.  With  refer- 
ence to  the  glass  of  the  experimental  tube,  and  the  air 
within  the  tube,  the  beam  employed  in  these  experiments 
was  perfectly  cold.  It  had  been  sifted  by  passing  it  through 
a  solution  of  alum,  and  through  the  thick  double-convex 
lens  of  the  lamp.  When  the  unsifted  beam  of  the  lamp 
was  employed,  the  effect  was  still  the  same ;  the  obscure 
calorific  rays  did  not  appear  to  interfere  with  the  result. 

My  object  here  being  simply  to  point  out  to  chemists  a 
method  of  experiment  which  reveals  a  new  and  beautiful 
series  of  reactions,  to  them  I  leave  the  examination  of  the 
products  of  decomposition.  The  molecule  of  the  nitrite  of 
amyl  is  obviously  shaken  asunder  by  certain  specific  waves 
of  the  electric  beam,  forming,  doubtless,  nitric  oxide  and 
other  products,  of  which  the  nitrate  of  amyl  is  probably 
one.  The  brown  fumes  of  nitrous  acid  were  also  seen  to 
mingle  with  the  cloud  within  the  experimental  tube. 
The  nitrate  of  amyl,  being  less  volatile  than  the  nitrite, 


DECOMPOSITION  BY  LIGHT.  97 

and  not  being  able  to  maintain  itself  in  the  condition  of 
vapour,  would  be  precipitated  as  a  visible  cloud  along  the 
track  of  the  beam. 

In  the  anterior  portions  of  the  tube  a  sifting  of  the  beam 
by  the  vapour  occurs,  which  diminishes  the  chemical  action 
in  the  posterior  portions.  In  some  experiments  the  pre- 
cipitated cloud  only  extended  halfway  down  the  tube. 
When,  under  these  circumstances,  the  lamp  was  shifted  so 
as  to  send  the  beam  through  the  other  end  of  the  tube, 
precipitation  occurred  there  also. 

Action  of  Sunlight. 

Solar  light  also  effects  the  decomposition  of  the  nitrite- 
of-amyl  vapour.  On  October  10  I  partially  darkened  a 
small  room  in  the  Eoyal  Institution,  into  which  the  sun 
shone,  permitting  the  light  to  enter  through  an  open 
portion  of  the  window-shutter.  In  the  track  of  the  beam 
was  placed  a  large  plano-convex  lens,  which  formed  a  fine 
convergent  cone  in  the  dust  of  the  room  behind  it.  The 
experimental  tube  was  filled  in  the  laboratory,  covered 
with  a  black  cloth,  and  carried  into  the  partially  darkened 
room.  On  thrusting  one  end  of  the  tube  into  the  cone  of 
rays  behind  the  lens,  precipitation  within  the  cone  was 
copious  and  immediate.  The  vapour  at  the  distant  end 
of  the  tube  was  in  part  shielded  by  that  in  front,  and  was 
also  more  feebly  acted  on  through  the  divergence  of  the 
rays.  On  reversing  the  tube,  a  second  and  similar  cone 
was  precipitated. 

Physical  Considerations. 

I  sought  to  determine  the  particular  portion  of  the 
white  beam  which  produced  the  foregoing  effects.  When, 
previous  to  entering  the  experimental  tube,  the  beam  was 
caused  to  pass  through  a  red  glass,  the  effect  was  greatly 


08  FRAGMENTS   OF   SCIENCE. 

weakened,  but  not  extinguished.  This  was  also  the  case 
with  various  samples  of  yellow  glass.  A  blue  glass  being 
introduced,  before  the  removal  of  the  yellow  or  the  red, 
on  taking  the  latter  away  augmented  precipitation  occurred 
along  the  truck  of  the  blue  beam.  Hence,  in  this  case, 
the  more  refrangible  rays  are  the  most  chemically  active. 

The  colour  of  the  liquid  nitrite  of  amyl  indicates  that 
this  must  be  the  case ;  it  is  a  feeble  but  distinct  yellow : 
in  other  words,  the  yellow  portion  of  the  beam  is  most 
freely  transmitted.  It  is  not,  however,  the  transmitted 
portion  of  any  beam  which  produces  chemical  action,  but 
the  absorbed  portion.  Blue,  as  the  complementary  colour 
to  yellow,  is  here  absorbed,  and  hence  the  more  energetic 
action  of  the  blue  rays.  This  reasoning,  however,  assumes 
that  the  same  rays  are  absorbed  by  the  liquid  and  its 
vapour. 

A  solution  of  the  yellow  chromate  of  potash,  the  colour 
of  which  may  be  made  almost,  if  not  altogether,  identical 
with  that  of  the  liquid  nitrite  of  amyl,  was  found  far  more 
effective  in  stopping  the  chemical  rays  than  either  the  red 
or  the  yellow  glass.  But  of  all  substances  the  nitrite  it- 
self is  most  potent  in  arresting  the  rays  which  act  upon 
its  vapour.  A  layer  one-eighth  of  an  inch  in  thickness, 
which  scarcely  preceptibly  affected  the  luminous  intensity, 
sufficed  to  absorb  the  entire  chemical  energy  of  the  con- 
centrated beam  of  the  electric  light. 

The  close  relation  subsisting  between  a  liquid  and  its 
vapour,  as  regards  their  action  upon  radiant  heat,  has  been 
already  amply  demonstrated.1  As  regards  the  nitrite  of 
amyl,  this  relation  is  more  specific  than  in  the  cases 
hitherto  adduced ;  for  here  the  special  constituent  of  the 
beam,  which  provokes  the  decomposition  of  the  vapour,  is 
shown  to  be  arrested  by  the  liquid. 

A  question  of  extreme  importance  in  molecular  physics 
1  'Phil.  Trans.'  1864;  and  p.  59  of  this  volume. 


DECOMPOSITION  BY  LIGHT.  09 

here  arises:  What  is  the  real  mechanism  of  this  absorp- 
tion, and  where  is  its  seat  ?  l 

I  figure,  as  others  do,  a  molecule  as  a  group  of  atoms, 
held  together  "by  their  mutual  forces,  but  still  capable  of 
motion  among  themselves.  The  vapour  of  the  nitrite  of 
amyl  is  to  be  regarded  as  an  assemblage  of  such  molecules. 
The  question  now  before  us  is  this :  In  the  act  of  absorp- 
tion, is  it  the  molecules  that  are  effective,  or  is  it  their 
constituent  atoms  ?  Is  the  vis  viva  of  the  intercepted 
light-waves  transferred  to  the  molecule  as  a  whole,  or  to 
its  constituent  parts  ? 

The  molecule,  as  a  whole,  can  only  vibrate  in  virtue 
of  the  forces  exerted  between  it  and  its  neighbour  mole- 
cules. The  intensity  of  these  forces,  and  consequently 
the  rate  of  vibration,  would,  in  this  case,  be  a  function  of 
the  distance  between  the  molecules.  Now  the  identical 
absorption  of  the  liquid  and  of  the  vaporous  nitrite  of  amyl 
indicates  an  identical  vibrating  period  on  the  part  of 
liquid  and  vapour,  and  this,  to  my  mind,  amounts  to  an 
experimental  demonstration  that  the  absorption  occurs 
in  the  main  within  the  molecule  For  it  can  hardly  be 
supposed,  if  the  absorption  were  the  act  of  the  molecule  as  a 
whole,  that  it  could  continue  to  affect  waves  of  the  same 
period  after  the  substance  had  passed  from  the  vaporous  to 
the  liquid  state. 

In  point  of  fact,  the  decomposition  of  the  nitrite  of 
amyl  is  itself  to  some  extent  an  illustration  of  this  in- 
ternal molecular  absorption  ;  for  were  the  absorption  the 
act  of  the  molecule  as  a  whole,  the  relative  motions  of  its 
constituent  atoms  would  remain  unchanged,  and  there 
would  be  no  mechanical  cause  for  their  separation.  It  is 
probably  the  synchronism  of  the  vibrations  of  one  portion 
of  the  molecule  with  the  incident  waves,  that  enables  the 

1  My  attention  was  very  forci  bly  directed  to  this  subject  some  years  ago 
by  a  conversation  with  my  excellent  friend  Professor  Clausius. 
7 


100  FRAGMENTS   OF   SCIENCE. 

amplitude  of  those  vibrations  to  augment,  until  the 
chain  which  binds  the  parts  of  the  molecule  together  is 
snapped  asunder. 

The  liquid  nitrite  of  amyl  is  probably  also  decomposed 
by  light ;  but  the  reaction,  if  it  exists,  is  incomparably  less 
rapid  and  distinct  than  that  of  the  vapour.  Nitrite  of 
amyl  has  been  subjected  to  the  concentrated  solar  rays 
until  it  boiled,  and  it  has  been  permitted  to  continue 
boiling  for  a  considerable  time,  without  any  distinctly 
apparent  change  occurring  in  the  liquid. 

I  anticipate  wide,  if  not  entire,  generality  for  the  fact 
that  a  liquid  and  its  vapour  absorb  the  same  rays.  A  cell 
of  liquid  chlorine  now  preparing  for  me  will,  I  imagine, 
deprive  light  more  effectually  of  its  power  of  causing 
chlorine  and  hydrogen  to  combine  than  any  other  filter  of 
the  luminous  rays.  The  rays  which  give  chlorine  its 
colour  have  nothing  to  do  with  this  combination,  those 
that  are  absorbed  by  the  chlorine  being  the  really  effec- 
tive rays.  A  highly  sensitive  bulb,  containing  chlorine 
and  hydrogen,  in  the  exact  proportions  necessary  for  the 
formation  of  hydrochloric  acid,  was  placed  at  one  end  of 
an  experimental  tube,  the  beam  of  the  electric  lamp 
being  sent  through  it  from  the  other.  The  bulb  did  not 
explode  when  the  tube  was  filled  with  chlorine,  while  the 
explosion  was  violent  and  immediate  when  the  tube  was 
filled  with  air.  I  anticipate  for  the  liquid  chlorine  an 
action  similar  to,  but  still  more  energetic  than,  that 
exhibited  by  the  gas.  If  this  should  prove  to  be  the  case,  it 
will  favour  the  view  that  chlorine  itself  is  molecular  and 
not  monatomic. 

Production  of  Sky-Hue  by  the  Decomp  sit  ion  of 
Nitrite  of  Amyl. 

When  the  quantity  of  nitrite  vapour  is  considerable, 
and  the  light  intense,  the  chemical  action  is  exceedingly 


DECOMPOSITION  BY  LIGHT.  101 

rapid,  the  particles  precipitated  being  so  large  as  to 
U'hiten  the  luminous  beam.  Not  so,  however,  when  a 
well-mixed  and  highly  attenuated  vapour  fills  the  experi- 
mental tube.  The  effect  now  to  be  described  was  first 
obtained  when  the  vapour  of  the  nitrite  was  derived 
from  a  portion  of  its  liquid,  accidentally  introduced  into 
the  passage  through  which  the  dry  air  flowed  into  the 
experimental  tube. 

In  this  case,  the  electric  beam  traversed  the  tube  for 
several  seconds  before  any  action  was  visible.  Decom- 
position then  visibly  commenced,  and  advanced  slowly. 
When  the  light  was  very  strong,  the  cloud  appeared  of  a 
milky  blue.  When,  on  the  contrary,  the  intensity  was 
moderate,  the  blue  was  pure  and  deep.  In  Briicke's  im- 
portant experiments  on  the  blue  of  the  sky  and  the  morn- 
ing and  evening  red,  pure  mastic  is  dissolved  in  alcohol, 
and  then  dropped  into  water  well  stirred.  When  the  pro- 
portion of  mastic  to  alcohol  is  correct,  the  resin  is  pre- 
cipitated so  finely  as  to  elude  the  highest  microscopic 
power.  By  reflected  light,  such  a  medium  appears  bluish, 
by  transmitted  light  yellowish,  which  latter  colour,  by 
augmenting  the  quantity  of  the  precipitate,  can  be  caused 
to  pass  into  orange  or  red. 

But  the  development  of  colour  in  the  attenuated 
nitrite-of-amyl  vapour,  though  admitting  of  the  same  ex- 
planation, is  doubtless  more  similar  to  what  takes  place 
in  our  atmosphere.  The  blue,  moreover,  is  far  purer  and 
more  sky-like  than  that  obtained  from  Briicke's  turbid 
medium.  Never,  even  in  the  skies  of  the  Alps,  have  I  seen 
a  richer  or  a  purer  blue  than  that  attainable  by  a  suitable 
disposition  of  the  light  falling  upon  the  precipitated 
vapour. 

In  exhausting  the  tube  containing  the  mixed  air  and 
nitrite-of-amyl  vapour,  it  was  difficult  to  avoid  explosions 
under  the  pistons  of  the  air-pump,  similar  to  those  which 


102         .  FEAGMENTS   OP   SCIENCE. 

I  have  already  described  as  occurring  with  the  vapours  of 
bisulphide  of  carbon  and  other  substances.  Though  the 
quantity  of  vapour  present  in  these  cases  must  have  been 
infinitesimal,  its  explosion  was  sometimes  sufficient  to  de- 
stroy the  valves  of  the  pump. 

Iodide  of  Allyl. — Among  the  liquids  hitherto  sub- 
jected to  the  concentrated  electric  light,  iodide  of  allyl, 
in  point  of  rapidity  and  intensity  of  action,  comes  next  to 
the  nitrite  of  amyl.  With  the  iodide  of  allyl  I  have  em- 
ployed both  oxygen  and  hydrogen,  as  well  as  air,  as  a 
vehicle,  and  found  the  effect  in  all  cases  substantially  the 
same.  The  cloud-column  here  was  exquisitely  beautiful. 
It  revolved  round  the  axis  of  the  decomposing  beam ;  it 
was  nipped  at  certain  places  like  an  hour-glass,  and  round 
the  two  bells  of  the  glass  delicate  cloud-filaments  twisted 
themselves  in  spirals.  It  also  folded  itself  into  convolu- 
tions resembling  those  of  shells.  In  certain  conditions  of 
the  atmosphere  in  the  Alps  I  have  often  observed  clouds  of 
a  special  pearly  lustre  ;  when  hydrogen  was  made  the 
vehicle  of  the  iodide-of-allyl  vapour  a  similar  lustre  was 
most  exquisitely  shown.  With  a  suitable  disposition  of 
the  light,  the  purple  hue  of  iodine-vapour  came  out  very 
strongly  in  the  tube. 

The  remark  already  made,  as  to  the  bearing  of  the 
decomposition  of  nitrite  of  amyl  by  light  on  the  question 
of  molecular  absorption,  applies  here  also ;  for  were  the 
absorption  the  work  of  the  molecule  as  a  whole,  the  iodine 
would  not  be  dislodged  from  the  allyl  with  which  it  is 
combined.  The  non-synchronism  of  iodine  with  the 
waves  of  obscure  heat  is  illustrated  by  its  marvellous 
transparency  to  such  heat.  May  not  its  synchronism 
with  the  waves  of  light  in  the  present  instance  be  the 
cause  of  its  divorce  from  the  allyl?  Further  experiments 
on  this  point  are  in  preparation. 

Iodide  of  Isopropyl. — The  action  of  light  upon  the 


DECOMPOSITION   BY   LIGHT.  103 

vapour  of  this  liquid  is,  at  first,  more  languid  than  upon 
iodide  of  allyl ;  indeed  many  beautiful  reactions  may  be 
overlooked,  in  consequence  of  this  languor  at  the  com- 
mencement. After  some  minutes'  exposure,  however, 
clouds  begin  to  form,  which  grow  in  density  and  in  beauty 
as  the  light  continues  to  act.  In  every  experiment 
hitherto  made  with  this  substance  the  column  of  cloud 
filling  the  experimental  tube,  was  divided  into  two  dis- 
tinct parts  near  the  middle  of  the  tube.  In  one  experi- 
ment a  globe  of  cloud  formed  at  the  centre,  from  which, 
right  and  left,  issued  an  axis  uniting  the  globe  with 
two  adjacent  cylinders.  Both  globe  and  cylinders  were 
animated  by  a  common  motion  of  rotation.  As  the  action 
continued,  paroxysms  of  motion  were  manifested;  the 
various  parts  of  the  cloud  would  rush  through  each  other 
with  sudden  violence.  During  these  motions  beautiful 
and  grotesque  cloud-forms  were  developed.  At  some  places 
the  nebulous  mass  would  become  ribbed  so  as  to  resemble 
the  graining  of  wood ;  a  longitudinal  motion  would  at 
times  generate  in  it  a  series  of  curved  transverse  bands, 
the  retarding  influence  of  the  sides  of  the  tube  causing  an 
appearance  resembling,  on  a  small  scale,  the  dirt-bands 
of  the  Mer  de  Glace.  In  the  anterior  portion  of  the  tube 
those  sudden  commotions  were  most  intense  ;  here  buds  of 
cloud  would  sprout  forth,  and  grow  in  a  few  seconds  in  to  per- 
fect flower-like  forms.  The  cloud  of  iodide  of  isopropyl  had 
a  character  of  its  own,  and  differed  materially  from  all 
others  that  I  had  seen.  A  gorgeous  mauve  colour  was 
observed  in  the  last  twelve  inches  of  the  tube ;  the  vapour 
of  iodine  was  present,  and  it  may  have  been  the  sky-blue 
scattered  by  the  precipitated  particles  which,  mingling 
with  the  purple  of  the  iodine,  produced  the  mauve.  As 
in  all  other  cases  here  adduced,  the  effects  were  proved 
to  be  due  to  the  light ;  they  never  occurred  in  darkness. 
The  forms  assumed  by  some  of  those  actinic  clouds, 


104  FRAGMENTS   OF   SCIENCE. 

in  consequence  of  rotations  and  other  motions,  due  to 
differences  of  temperature,  are  perfectly  astounding.  I 
content  myself  here  with  a  meagre  description  of  one 
more  of  them. 

The  tube  being  filled  with  the  sensitive  mixture,  the 
beam  was  sent  through  it,  the  lens  at  the  same  time 
being  so  placed  as  to  produce  a  cone  of  very  intense  light. 
Two  minutes  elapsed  before  anything  was  visible  ;  but  at 
the  end  of  this  time  a  faint  bluish  cloud  appeared  to  hang 
itself  on  the  most  concentrated  portion  of  the  beam. 

Soon  afterwards  a  second  cloud  was  formed  five  inches 
farther  down  the  experimental  tube.  Both  clouds  were 
united  by  a  slender  cord  of  the  same  bluish  tint  as  them- 
selves. 

As  the  action  of  the  light  continued,  the  first  cloud 
gradually  resolved  itself  into  a  series  of  parallel  disks  of 
exquisite  delicacy,  which  rotated  round  an  axis  perpen- 
dicular to  their  surfaces,  and  finally  blended  to  a  screw 
surface  with  an  inclined  generatrix.  This  gradually 
changed  into  a  filmy  funnel,  from  the  narrow  end  of 
which  the  '  cord '  extended  to  the  cloud  in  advance.  The 
latter  also  underwent  slow  but  incessant  modification.  It 
first  resolved  itself  into  a  series  of  strata  resembling  those 
of  the  electric  discharge.  After  a  little  time,  and  through 
changes  which  it  was  difficult  to  follow,  both  clouds  pre- 
sented the  appearance  of  a  series  of  concentric  funnels 
set  one  within  the  other,  the  interior  ones  being  seen 
through  the  outer  ones.  Those  of  the  distant  cloud  re- 
sembled claret-glasses  in  shape.  As  many  as  six  funnels 
were  thus  concentrically  set  together,  the  two  series 
being  united  by  the  delicate  cord  of  cloud,  already  re- 
ferred to.  Other  cords  and  slender  tubes  were  afterwards 
formed,  which  coiled  themselves  in  delicate  spirals  around 
the  funnels. 

Eendering  the  light  along  the  connecting-cord  more 


ARTIFICIAL   SKY.  105 

intense,  it  diminished  in  thickness  and  became  whiter ; 
this  was  a  consequence  of  the  enlargement  of  its  particles. 
The  cord  finally  disappeared,  while  the  funnels  melted 
into  two  ghost-like  films,  shaped  like  parasols.  They 
were  barely  visible,  being  of  an  exceedingly  delicate  blue 
tint.  They  seemed  woven  of  blue  air.  To  compare  them 
with  cobweb  or  with  gauze  would  be  to  liken  them  to 
something  infinitely  grosser  than  themselves. 

In  all  cases  a  distant  candle-flame,  when  looked  at 
through  the  cloud,  was  sensibly  undimmed. 

§  2.  ON  THE  BLUE  COLOUR  OF  THE  SKY,  AND  THE 
POLARISATION  OF  SKYLIGHT.' 

1869. 

After  the  communication  of  the  foregoing  brief  abstract 
'On  a  new  Series  of  Chemical  Reactions  produced  by 
Light,'  the  experiments  upon  this  subject  were  continued, 
the  number  of  substances  thus  acted  on  being  considerably 
increased. 

I  now  beg  to  direct  attention  to  two  questions  glanced 
at  incidentally  in  the  abstract  referred  to — the  blue 
colour  of  the  sky,  and  the  polarisation  of  skylight.  Re- 
serving the  historic  treatment  of  the  subject  for  a  more 
fitting  occasion,  I  would  merely  mention  now  that  these 
questions  constitute,  in  the  opinion  of  our  most  eminent 
authorities,  the  two  great  standing  enigmas  of  meteor- 
ology. Indeed  it  was  the  interest  manifested  in  them 
by  Sir  John  Herschel,  in  a  letter  of  singular  speculative 
power,  addressed  to  myself,  that  caused  me  to  enter  upon 
the  consideration  of  these  questions  so  soon. 

The  apparatus  with  which  I  work  consists,  as  already 
stated,  of  a  glass  tube  about  a  yard  in  length,  and  from 

1  In  my  '  Lectures  on  Light '  (Longmans),  the  polarisation  of  light  will 
be  found  briefly,  but,  I  trust,  clearly  explained. 


106  FRAGMENTS    OF   SCIENCE. 

2£  to  3  inches  internal  diameter.  The  vapour  to  be 
examined  is  introduced  into  this  tube  in  the  manner  de- 
scribed in  my  last  abstract,  and  upon  it  the  condensed  beam 
of  the  electric  lamp  is  permitted  to  act,  until  the  neutrality 
or  the  activity  of  the  substance  has  been  declared. 

It  has  hitherto  been  my  aim  to  render  the  chemical 
action  of  light  upon  vapours  visible.  For  this  purpose 
substances  have  been  chosen,  one  at  least  of  whose  pro- 
ducts of  decomposition  under  light  shall  have  a  boiling- 
point  so  high,  that  as  soon  as  the  substance  is  formed  it 
shall  be  precipitated.  By  graduating  the  quantity  of  the 
vapour,  this  precipitation  may  be  rendered  of  any  degree 
of  fineness,  forming  particles  distinguishable  by  the 
naked  eye,  or  far  beyond  the  reach  of  our  highest  micro- 
scopic powers. 

I  have  no  reason  to  doubt  that  particles  may  be  thus 
obtained,  whose  diameters  constitute  but  a  small  fraction 
of  the  length  of  a  wave  of  violet  light. 

In  all  cases  when  the  vapours  of  the  liquids  employed 
are  sufficiently  attenuated,  no  matter  what  the  liquid 
may  be,  the  visible  action  commences  with  the  formation 
of  a  blue  cloud.  I  would  guard  myself  at  the  outset 
against  all  misconception  as  to  the  use  of  this  term.  The 
*  cloud '  here  referred  to  is  totally  invisible  in  ordinary 
daylight.  To  be  seen,  it  requires  to  be  surrounded  by 
darkness,  it  only  being  illuminated  by  a  powerful  beam 
of  light.  This  blue  cloud  differs  in  many  important 
particulars  from  the  finest  ordinary  clouds,  and  might 
justly  have  assigned  to  it  an  intermediate  position  between 
such  clouds  and  true  vapour. 

With  this  explanation,  the  term  '  cloud,'  or  « incipient 
cloud,'  as  I  propose  to  employ  it,  cannot,  I  think,  be  mis- 
understood. 

I  had  been  endeavouring  to  decompose  carbonic  acid 


ARTIFICIAL  SKY.  JOT 

gas  by  light.  A  faint  bluish  cloud,  due  it  may  be,  or  it 
may  not  be,  to  the  residue  of  some  vapour  previously 
employed,  was  formed  in  the  experimental  tube.  On 
looking  across  this  cloud  through  a  Nicol's  prism,  the  line 
of  vision  being  horizontal,  it  was  found  that  when  the 
short  diagonal  of  the  prism  was  vertical,  the  quantity  of 
light  reaching  the  eye  was  greater  than  when  the  long 
diagonal  was  vertical. 

When  a  plate  of  tourmaline  was  held  between  the  eye 
and  the  bluish  cloud,  the  quantity  of  light  reaching  the  eye 
when  the  axis  of  the  prism  was  perpendicular  to  the  axis 
of  the  illuminating  beam,  was  greater  than  when  the  axes 
of  the  crystal  and  of  the  beam  were  parallel  to  each  other. 

This  was  the  result  all  round  the  experimental  tube. 
Causing  the  crystal  of  tourmaline  to  revolve  round  the 
tube,  with  its  axis  perdendicular  to  the  illuminating 
beam,  the  quantity  of  light  that  reached  the  eye  was  in 
all  its  positions  a  maximum.  When  the  crystallographic 
axis  was  parallel  to  the  axis  of  the  beam,  the  quantity  of 
light  transmitted  by  the  crystal  was  a  minimum. 

From  the  illuminated  bluish  cloud,  therefore,  polarised 
light  was  discharged,  the  direction  of  maximum  polarisa- 
tion being  at  right  angles  to  the  illuminating  beam  ;  the 
plane  of  vibration  of  the  polarised  light  was  perpendicular 
to  the  beam.1 

Thin  plates  of  selenite  or  of  quartz,  placed  between 
the  Nicol  and  the  bluish  cloud,  displayed  the  colours  of 
polarised  light,  these  colours  being  most  vivid  when  the 
line  of  vision  was  at  right  angles  to  the  experimental 
tube.  The  plate  of  selenite  usually  employed  was  a 

1  This  is  still  an  undecided  point ;  but  the  probabilities  are  so  much  in 
its  favour,  and  it  is  in  my  opinion  so  much  preferable  to  have  a  physical 
image  on  -which  the  mind  can  rest,  that  I  do  not  hesitate  to  employ  the 
phraseology  in  the  text. 


108  FRAGMENTS   OF   SCIENCE. 

circle,  thinnest  at  the  centre,  and  augmenting  uniformly 
in  thickness  from  the  centre  outwards.  When  placed  in 
its  proper  position  between  the  Nicol  and  the  cloud,  it 
exhibited  a  system  of  splendidly-coloured  rings. 

The  cloud  here  referred  to  was  the  first  operated  upon 
in  the  manner  described.  It  may,  however,  be  greatly 
improved  upon  by  the  choice  of  proper  substances,  and 
by  the  application,  in  proper  quantities,  of  the  substances 
chosen.  Benzol,  bisulphide  of  carbon,  nitrite  of  amyl, 
nitrite  of  butyl,  iodide  of  allyl,  iodide  of  isopropyl,  and 
many  other  substances  may  be  employed.  I  will  take 
the  nitrite  of  butyl  as  illustrative  of  the  means  adopted 
to  secure  the  best  result,  with  reference  to  the  present 
question. 

And  here  it  may  be  mentioned  that  a  vapour,  which 
when  alone,  or  mixed  with  air  in  the  experimental  tube, 
resists  the  action  of  light,  or  shows  but  a  feeble  result  of 
this  action,  may,  when  placed  in  proximity  with  another 
gas  or  vapour,  exhibit  vigorous,  if  not  violent  action.  The 
case  is  similar  to  that  of  carbonic  acid  gas,  which,  diffused 
in  the  atmosphere,  resists  the  decomposing  action  of  solar 
light,  but  when  placed  in  contiguity  with  chlorophyl  in 
the  leaves  of  plants,  has  its  molecules  shaken  asunder. 

Dry  air  was  permitted  to  bubble  through  the  liquid 
nitrite  of  butyl,  until  the  experimental  tube,  which  had 
been  previously  exhausted,  was  filled  with  the  mixed  air 
and  vapour.  The  visible  action  of  light  upon  the  mix- 
ture after  fifteen  minutes'  exposure  was  slight.  The  tube 
was  afterwards  filled  with  half  an  atmosphere  of  the  mixed 
air  and  vapour,  and  a  second  half-atmosphere  of  air  which 
had  been  permitted  to  bubble  through  fresh  commercial 
hydrochloric  acid.  On  sending  the  beam  through  this 
mixture,  the  tube,  for  a  moment,  was  optically  empty. 
But  the  pause  amounted  only  to  a  small  fraction  of  a 


ARTIFICIAL   SKY.  109 

second,  a  dense  cloud  being  immediately  precipitated  upon 
the  beam. 

This  cloud  began  blue,  but  the  advance  to  whiteness 
was  so  rapid  as  almost  to  justify  the  application  of  the 
term  instantaneous.  The  dense  cloud,  looked  at  perpen- 
dicularly to  its  axis,  showed  scarcely  any  signs  of  polari- 
sation. Looked  at  obliquely  the  polarisation  was  strong. 

The  experimental  tube  being  again  cleansed  and  ex- 
hausted, the  mixed  air  and  nitrite-of-butyl  vapour  was 
permitted  to  enter  it  until  the  associated  mercury  column 
was  depressed  ^  of  an  inch.  In  other  words,  the  air  and 
vapour,  united,  exercised  a  pressure  not  exceeding  -3^  of 
an  atmosphere.  Air,  passed  through  a  solution  of  hydro- 
chloric acid,  was  then  added,  till  the  mercury  column  was 
depressed  three  inches.  The  condensed  beam  of  the  elec- 
tric light  passed  for  some  time  in  darkness  through  this 
mixture.  There  was  absolutely  nothing  within  the  tube 
competent  to  scatter  the  light.  Soon,  however,  a  superbly 
blue  cloud  was  formed  along  the  track  of  the  beam,  and  it 
continued  blue  sufficiently  long  to  permit  of  its  thorough 
examination.  The  light  discharged  from  the  cloud,  at 
right  angles  to  its  own  length,  was  perfectly  polarised. 
By  degrees  the  cloud  became  of  whitish  blue,  and  for  a 
time  the  selenite  colours,  obtained  by  looking  at  it  nor- 
mally were  exceedingly  brilliant.  The  direction  of  maxi- 
mum polarisation  was  distinctly  at  right  angles  to  the 
illuminating  beam.  This  continued  to  be  the  case  as  long 
as  the  cloud  maintained  a  decided  blue  colour,  and  even 
for  some  time  after  the  pure  blue  had  changed  to  whitish 
blue.  But,  as  the  light  continued  to  act,  the  cloud  became 
coarser  and  whiter,  particularly  at  its  centre,  where  it  at 
length  ceased  to  discharge  polarised  light  in  the  direction 
of  the  perpendicular,  while  it  continued  to  do  so  at  both 
its  endg 


110  FRAGMENTS   OF   SCIENCE. 

But  the  cloud  which  had  thus  ceased  to  polarise  the 
light  emitted  normally,  showed  vivid  selenite  colours  when 
looked  at  obliquely,  proving  that  the  direction  of  maxi- 
mum polarisation  changed  with  the  texture  of  the 
cloud.  This  point  shall  receive  further  illustration  subse- 
quently. 

A  blue,  equally  rich  and  more  durable,  was  obtained 
by  employing  the  nitrite-of-butyl  vapour  in  a  still  more 
attenuated  condition.  Now  the  instance  here  cited  is  re- 
presentative. In  all  cases,  and  with  all  substances,  the 
cloud  formed  at  the  commencement,  when  the  precipitated 
particles  are  sufficiently  fine,  is  blue,  and  it  can  be  made 
to  display  a  colour  rivalling  that  of  the  purest  Italian  sky. 
In  all  cases,  moreover,  this  fine  blue  cloud  polarises  per- 
fectly the  beam  which  illuminates  it,  the  direction  of 
polarisation  enclosing  an  angle  of  90°  with  the  axis  of  the 
illuminating  beam. 

It  is  exceedingly  interesting  to  observe  both  the  per- 
fection and  the  decay  of  this  polarisation.  For  ten  or  fifteen 
minutes  after  its  first  appearance  the  light  from  a  vividly 
illuminated  incipient  cloud,  looked  at  perpendicularly,  is 
absolutely  quenched  by  a  Nicol's  prism  with  its  longer 
diagonal  vertical.  But  as  the  sky-blue  is  gradually  ren- 
dered impure  by  the  introduction  of  particles  of  too  large 
a  size — in  other  words,  as  real  clouds  begin  to  be  formed — 
the  polarisation  begins  to  deteriorate,  a  portion  of  the 
light  passing  through  the  prism  in  all  its  positions.  It  is 
worthy  of  note,  that  for  some  time  after  the  cessation  of 
perfect  polarisation,  the  residual  light  which  passes,  when 
the  Nicol  is  in  its  position  of  minimum  transmission,  is  of 
a  gorgeous  blue,  the  whiter  light  of  the  cloud  being  ex- 
tinguished.1 When  the  cloud  texture  has  become  suffici 
ently  coarse  to  approximate  to  that  of  ordinary  clouds,  the 

1  This  shows  that  particles  too  Urge  to  polarise  the  Llue,  polarise 
perfectly  light  of  lower  refrangibility. 


ARTIFICIAL   SKY.  Ill 

rotation  of  the  Nicol  ceases  to  have  any  sensible  effect  on 
the  quantity  of  light  discharged  normally. 

The  perfection  of  the  polarisation,  in  a  direction  per- 
pendicular to  the  illuminating  beam,  is  also  illustrated  by 
the  following  experiment :  A  Nicol's  prism,  large  enough 
to,  embrace  the  entire  beam  of  the  electric  lamp,  was 
placed  between  the  lamp  and  the  experimental  tube.  A 
few  bubbles  of  air,  carried  through  the  liquid  nitrite  of 
butyl,  were  introduced  into  the  tube,  and  they  were  fol- 
lowed by  about  three  inches  (measured  by  the  mercurial 
gauge)  of  air  which  had  passed  through  aqueous  hydro- 
chloric acid.  Sending  the  polarised  beam  through  the 
tube,  I  placed  myself  in  front  of  it,  my  eye  being  on  a 
level  with  its  axis,  my  assistant  Mr.  Cottrell  occupying  a 
similar  position  behind  the  tube.  The  short  diagonal  of 
the  large  Nicol  was  in  the  first  instance  vertical,  the  plane 
of  vibration  of  the  emergent  beam  being  therefore  also 
vertical.  As  the  light  continued  to  act,  a  superb  blue 
cloud,  visible  to  both  my  assistant  and  myself,  was  slowly 
formed.  But  this  cloud,  so  deep  and  rich  when  looked  at 
from  the  positions  mentioned,  utterly  disappeared  when 
looked  at  vertically  downwards,  or  vertically  upwards. 
Reflection  from  the  cloud  was  not  possible  in  these  direc- 
tions. When  the  large  Nicol  was  slowly  turned  round  its 
axis,  the  eye  of  the  observer  being  on  the  level  of  the 
beam,  and  the  line  of  vision  perpendicular  to  it,  entire 
extinction  of  the  light  emitted  horizontally  occurred  when 
the  longer  diagonal  of  the  large  Nicol  was  vertical.  But 
now  a  vivid  blue  cloud  was  seen  when  looked  at  down- 
wards or  upwards.  This  truly  fine  experiment  was  first 
definitely  suggested  by  a  remark  in  a  letter  addressed 
so  me  by  Professor  Stokes. 

As  regards  the  polarisation  of  skylight,  the  greatest 
stumbling-block  has  hitherto  been,  that,  in  accordance  with 
the  law  of  Brewster,  which  makes  the  index  of  refraction 


112  FRAGMENTS   OF  SCIENCE 

the  tangent  of  the  polarising  angle,  the  reflection  which 
produces  perfect  polarisation  would  require  to  be  made  in 
air  upon  air  ;  and  indeed  this  led  many  of  our  most  emi- 
nent men,Brewster  himself  among  the  number,  to  entertain 
the  idea  of  aerial  molecular  reflection.1  I  have,  however, 
operated  upon  substances  of  widely  different  refractive 
indices,  and  therefore  of  very  different  polarising  angles 
as  ordinarily  defined,  but  the  polarisation  of  the  beam,  by 
the  incipient  cloud,  has  thus  far  proved  itself  to  be  abso- 
lutely independent  of  the  polarising  angle.  The  law  of 
Brewster  does  not  apply  to  matter  in  this  condition,  and 
it  rests  with  the  undulatory  theory  to  explain  why. 
Whenever  the  precipitated  particles  are  sufficiently  fine, 
no  matter  what  the  substance  forming  the  particles  may 
be,  the  direction  of  maximum  polarisation  is  at  right 
angles  to  the  illuminating  beam,  the  polarising  angle  for 
matter  in  this  condition  being  invariably  45°. 

Suppose  our  atmosphere  surrounded  by  an  envelope  im- 
pervious to  light.  But  with  an  aperture  on  the  sunward 
side,  through  which  a  parallel  beam  of  solar  light  could 
enter  and  traverse  the  atmosphere.  Surrounded  by  air 

1  '  The  cause  of  the  polarisation  is  evidently  a  reflection  of  the  sun's 
light  upon  something.  The  question  is  on  •what?  Were  the  angle  of 
maximum  polarisation  76°,  we  should  look  to  water  or  ice  as  the  reflecting 
body,  however  inconceivable  the  existence  in  a  cloudless  atmosphere,  and  a 
hot  summer's  day  of  unevaporated  molecules  (particles  ?),  of  water.  But 
though  we  were  once  of  this  opinion,  careful  observation  has  satisfied  us  that 
90°,  or  thereabouts,  is  the  correct  angle,  and  that  therefore  whatever  be  the 
body  on  which  the  light  has  been  reflected,  if  polarised  by  a  single  reflection, 
the  polarising  angle  must  be  45°,  and  the  index  of  refraction,  which  is  the 
tangent  of  that  angle,  unity ;  in  other  words,  the  reflection  would  require 
to  be  made  in  air  upon  air ! '  (Sir  John  Hersehel,  '  Meteorology,"  par. 
233.) 

Any  particles,  if  small  enough,  will  produce  both  the  colour  and  the 
polarisation  of  the  sky.  But  is  the  existence  of  small  water-particles  on  a 
hot  summer's  day  in  the  higher  regions  of  our  atmosphere  inconceivable? 
It  is  to  be  remembered  that  the  oxygen  and  nitrogen  of  the  air  behave  as 
a  vacuum  to  radiant  heat,  the  exceedingly  attenuated  vapour  of  the  higher 
atmosphere  being  therefore  in  practical  contact  with  the  cold  of  spaco. 


ARTIFICIAL   SKY.  113 

not  directly  illuminated,  the  track  of  such  a  beam  through 
the  air  would  resemble  that  of  the  parallel  beam  of  the 
electric  lamp  through  an  incipient  cloud.  The  sunbeam 
would  be  blue,  and  it  would  discharge  laterally  light  in 
precisely  the  same  condition  as  that  discharged  by  the  in- 
cipient cloud.  In  fact,  the  azure  revealed  by  such  a  beam 
would  be  to  all  intents  and  purposes  that  which  I  have 
called  a  'blue  cloud.'  Conversely  our  'blue  cloud'  is, 
to  all  intents  and  purposes,  an  artificial  sky.1 

But,  as  regards  the  polarisation  of  the  sky,  we  know 
that  not  only  is  the  direction  of  maximum  polarisation  at 
right  angles  to  the  track  of  the  solar  beams,  but  that  at 
certain  angular  distances,  probably  variable  ones,  from 
the  sun,  '  neutral  points,'  or  points  of  no  polarisation, 
exist,  on  both  sides  of  which  the  planes  of  atmospheric 
polarisation  are  at  right  angles  to  each  other. 

I  have  made  various  observations  upon  this  subject 
which  are  reserved  for  the  present ;  but,  pending  the  more 
complete  examination  of  the  question,  the  following  facts 
bearing  upon  it  may  be  submitted. 

The  parallel  beam  employed  in  these  experiments 
tracked  its  way  through  the  laboratory  air,  exactly  as  sun- 
beams are  seen  to  do  in  the  dusty  air  of  London.  I  have 
reason  to  believe  that  a  great  portion  of  the  matter  thus 
floating  in  the  laboratory  air  consists  of  organic  particles, 

1  The  opinion  of  Sir  John  Herschel,  connecting  the  polarisation  and 
the  blue  colour  of  the  sky  is  verified  by  the  foregoing  results.  '  The  more 
the  subject  [the  polarisation  of  skylight]  is  considered,'  writes  this  eminent 
philosopher,  '  the  more  it  -will  be  found  beset  with  difficulties,  and  its  ex- 
planation when  arrived  at  will  probably  be  found  to  carry  with  it  that  of 
the  blue  colour  of  the  sky  itself,  and  of  the  great  quantity  of  light  it  actually 
does  send  down  to  us.'  '  We  may  observe,  too,'  he  adds,  '  that  it  is  only 
where  the  purity  of  the  sky  is  most  absolute  that  the  polarisation  is 
developed  in  its  highest  degree,  and  that  where  there  is  the  slightest  per- 
ceptible tendency  to  cirrus  it  is  materially  impaired."  This  applies  word 
for  word  to  our  '  incipient  clouds.' 


114  FRAGMENTS   OF   SCIENCE. 

which  are  capable  of  imparting  a  perceptibly  bluish  tint 
to  the  air.  These  also  showed,  though  far  less  vividly,  all 
the  effects  of  polarisation  obtained  with  the  incipient 
clouds.  The  light  discharged  laterally  from  the  track  of 
the  illuminating  beam  was  polarised,  though  not  perfectly, 
the  direction  of  maximum  polarisation  being  at  right 
angles  to  the  beam. 

The  horizontal  column  of  air,  thus  illuminated,  was  1 8 
feet  long,  and  could  therefore  be  looked  at  very  obliquely. 
At  all  points  of  the  beam,  throughout  its  entire  length, 
the  light  emitted  normally  was  in  the  same  state  of  polar- 
isation. Keeping  the  positions  of  the  Nicol  and  the 
selenite  constant,  the  same  colours  were  observed  through- 
out the  entire  beam,  when  the  line  of  vision  was  perpen- 
dicular to  its  length. 

I  then  placed  myself  near  the  end  of  the  beam,  as  it 
issued  from  the  electric  lamp,  and,  looking  through  the 
Nicol  and  selenite  more  and  more  obliquely  at  the  beam, 
observed  the  colours  fading  until  they  disappeared.  Aug- 
menting the  obliquity  the  colours  appeared  once  more, 
but  they  were  now  complementai~y  to  the  former  ones. 

Hence  this  beam,  like  the  sky,  exhibited  a  neutral 
point,  on  opposite  sides  of  which  the  light  was  polarised 
in  planes  at  right  angles  to  each  other. 

Thinking  that  the  action  observed  in  the  laboratory 
might  be  caused,  in  some  way,  by  the  vaporous  fumes  dif- 
fused in  its  air,  I  had  the  light  removed  to  a  room  at  the 
top  of  the  Eoyal  Institution.  The  track  of  the  beam  was 
seen  very  finely  in  the  air  of  this  room,  a  length  of  14 
or  15  feet  being  attainable.  This  beam  exhibited  all  the 
effects  observed  with  the  beam  in  the  laboratory.  Even 
the  uncondensed  electric  light  falling  on  the  floating 
matter  showed,  though  faintly,  the  effects  of  polarisation. 

When  the  air  was  so  sifted  as  to  entirely  remove  the 
visible  floating  matter,  it  no  longer  exerted  any  sensible 


AKTIFICIAL   SKY.  115 

action  upon  the  light,  but  behaved  like  a  vacuum.  The 
light  is  scattered  by  particles,  not  by  molecules  or 
atoms. 

By  operating  upon  the  fumes  of  chloride  of  ammo- 
nium, the  smoke  of  brown  paper,  and  tobacco-smoke,  I 
had  varied  and  confirmed  in  many  ways  those  experiments 
on  neutral  points,  when  my  attention  was  drawn  by  Sir 
Charles  Wheatstone  to  an  important  observation  communi- 
cated to  the  Paris  Academy  in  1860  by  Professor  Govi, 
of  Turin.1  M.  Govi  had  been  led  to  examine  a  beam  of 
light  sent  through  a  room  in  which  was  diffused  the 
smoke  of  incense,  and  tobacco-smoke.  His  first  brief 
communication  stated  the  fact  of  polarisation  by  such 
smoke ;  but  in  his  second  communication  he  announced 
the  discovery  of  a  neutral  point  in  the  beam,  at  the 
opposite  sides  of  which  the  light  was  polarised  in  planes 
at  right  angles  to  each  other. 

But  unlike  my  observations  on  the  laboratory  air,  and 
unlike  the  action  of  the  sky,  the  direction  of  maximum 
polarisation  in  M.  Govi's  experiment  enclosed  a  very  small 
angle  with  the  axis  of  the  illuminating  beam.  The  ques- 
tion was  left  in  this  condition,  and  I  am  not  aware  that 
M.  Govi  or  any  other  investigator  has  pursued  it  further. 

I  had  noticed,  as  before  stated,  that  as  the  clouds 
formed  in  the  experimental  tube  became  denser,  the  polar- 
isation of  the  light  discharged  at  right  angles  to  the  beam 
became  weaker,  the  direction  of  maximum  polarisation 
becoming  oblique  to  the  beam.  Experiments  on  the 
fumes  of  chloride  of  ammonium  gave  me  also  reason  to 
suspect  that  the  position  of  the  neutral  point  was  not  con- 
stant, but  that  it  varied  with  the  density  of  the  illumin- 
ated fumes. 

The  examination  of  these  questions  led  to  the  follow- 

1  '  Comptes  Kandus,'  tome  li.  pp.  360  and  669. 


116  FRAGMEOTS   OP   SCIENCE. 

ing  new  and  remarkable  results :  The  laboratory  being 
well  filled  with  the  fumes  of  incense,  and  sufficient  time 
being  allowed  for  their  uniform  diffusion,  the  electric 
beam  was  sent  through  the  smoke.  From  the  track  of 
the  beam  polarised  light  was  discharged ;  but  the  direction 
of  maximum  polarisation,  instead  of  being  perpendicular, 
now  enclosed  an  angle  of  only  12°  or  13°  with  the  axis  of 
the  beam. 

A  neutral  point,  with  complementary  effects  at  oppo- 
site sides  of  it,  was  also  exhibited  by  the  beam.  The 
angle  enclosed  by  the  axis  of  the  beam,  and  a  line  drawn 
from  the  neutral  point  to  the  observer's  eye,  measured  in 
the  first  instance  66°. 

The  windows  of  the  laboratory  were  now  opened  for  some 
minutes,  a  portion  of  the  incense-smoke  being  permitted 
to  escape.  On  again  darkening  the  room  and  turning 
on  the  light,  the  line  of  vision  to  the  neutral  point  was 
found  to  enclose,  with  the  axis  of  the  beam,  an  angle 
of  63°. 

The  windows  were  again  opened  for  a  few  minutes, 
more  of  the  smoke  being  permitted  to  escape.  Measured 
as  before,  the  angle  referred  to  was  found  to  be  54°. 

This  process  was  repeated  three  additional  times  ;  the 
neutral  point  was  found  to  recede  lower  and  lower  down 
the  beam,  the  angle  between  a  line  drawn  from  the  eye  to 
the  neutral  point  and  the  axis  of  the  beam  falling  succes- 
sively from  54°  to  49°,  43°  and  33°. 

The  distances,  roughly  measured,  of  the  neutral  point 
from  the  lamp,  corresponding  to  the  foregoing  series  of 
observations,  were  these : — 


1st  observation   . 

2  feet    2  inches. 

2nd 

2     „      6     „ 

3rd 

2     „    10     „ 

4th 

3     „      2     „ 

5th 

3     „      7     „ 

6th 

*     »      6     „ 

ARTIFICIAL   SKY.  117 

At  the  end  of  this  series  of  experiments  the  direction 
of  maximum  polarisation  had  again  become  normal  to  the 
beam. 

The  laboratory  was  next  filled  with  the  fumes  of  gun- 
powder. In  five  successive  experiments,  corresponding 
to  five  different  densities  of  the  gunpowder-smoke,  the 
angles  enclosed  between  the  line  of  vision  to  the  neutral 
point,  and  the  axis  of  the  beam,  were  63°,  50°,  47°,  42°, 
and  38°  respectively. 

After  the  clouds  of  gunpowder  had  cleared  away  the 
laboratory  was  filled  with  the  fumes  of  common  resin, 
rendered  so  dense  as  to  be  very  irritating  to  the  lungs. 
The  direction  of  maximum  polarisation  enclosed,  in  this 
case,  an  angle  of  12°,  or  thereabouts,  with  the  axis  of  the 
beam.  Looked  at,  as  in  the  former  instances,  from  a  posi- 
tion near  the  electric  lamp,  no  neutral  point  was  observed 
throughout  the  entire  extent  of  the  beam. 

When  this  beam  was  looked  at  normally  through  the 
selenite  and  Nicol,  the  ring-system,  though  not  brilliant, 
was  distinct.  Keeping  the  eye  upon  the  plate  of  selenite, 
and  the  line  of  vision  perpendicular,  the  windows  were 
opened,  the  blinds  remaining  undrawn.  The  resinous 
fumes  slowly  diminished,  and  as  they  did  so  the  ring-system 
became  paler.  It  finally  disappeared.  Continuing  to 
look  in  the  same  direction,  the  rings  revived,  but  now  the 
colours  were  complementary  to  the  former  ones.  The  neu- 
tral point  had  passed  me  in  its  motion  down  the  beam, 
consequent  upon  the  attenuation  of  the  fumes  of  resin. 

With  the  fumes  of  chloride  of  ammonium  substantially 
the  same  results  were  obtained.  Sufficient,  however,  has 
been  here  stated  to  illustrate  the  variability  of  the  position 
of  the  neutral  point.1 

1  Brewster  has  proved  the  variability  of  the  position  of  the  neutral 
point  for  skylight  with  the  sun's  altitude,  a  result  obviously  connected  with 
the  foregoing  experiments. 


118  FRAGMENTS   OP   SCIENCE. 

Some  of  the  clouds  formed  in  the  experiments  on 
the  chemical  action  of  light  are,  as  already  stated,  aston- 
ishing as  to  shape.  The  experimental  tube  is  often  divided 
into  segments  of  dense  cloud,  separated  from  each  other 
by  nodes  of  finer  matter.  Looked  at  normally,  as  many 
as  four  reversals  of  the  plane  of  polarisation  have  been 
found,  in  passing  from  node  to  segment,  and  from  seg- 
ment to  node.  With  the  fumes  diffused  in  the  laboratory, 
on  the  contrary,  there  was  no  change  in  the  polarisation 
along  the  normal,  for  here  the  necessary  differences  of 
cloud-texture  did  not  exist. 

By  a  puff  of  tobacco-smoke,  or  of  condensed  steam, 
blown  into  the  illuminated  beam,  the  brilliancy  of  the 
selenite  colours  may  be  greatly  augmented.  But  with 
different  clouds  two  different  effects  are  produced.  Let 
the  ring-system  observed  in  the  common  air  be  brought 
to  its  maximum  strength,  and  then  let  an  attenuated 
cloud  of  chloride  of  ammonium  be  thrown  into  the 
beam  at  the  point  looked  at;  the  ring-system  flashes 
out  with  augmented  brilliancy,  but  the  character  of  the 
polarisation  remains  unchanged.  This  is  also  the  case 
when  phosphorus,  or  sulphur,  is  burned  underneath  the 
beam,  so  as  to  cause  the  fine  particles  of  phosphoric  acid 
or  of  sulphur  to  rise  into  the  light.  With  the  sulphur- 
fumes  the  brilliancy  of  the  colours  is  exceedingly  intensi- 
fied ;  but  in  none  of  these  cases  is  there  any  change  in  the 
character  of  the  polarisation. 

But  when  a  puff  of  aqueous  cloud,  or  of  the  fumes  of 
hydrochloric  acid,  hydriodic  acid,  or  nitric  acid  is  thrown 
into  the  beam,  there  is  a  complete  reversal  of  the  selenite 
tints.  Each  of  these  clouds  twists  the  plane  of  polarisa- 
tion 90°.  On  these  and  kindred  points  experiments  are 
still  in  progress.1 

1  Sir  John  Herschel  suggested  to  me  that  this  change  of  the  polar- 
isation from  positive  to  negative  may  indicate  a  change  from  polarisation 


ARTIFICIAL   SKY.  119 

Almost  all  liquids  have  motes  in  them  sufficiently  nu- 
merous to  polarise  sensibly  the  light,  and  \rery  beautiful 
effects  may  be  obtained  by  simple  artificial  devices. 
When,  for  example,  a  cell  of  distilled  water  is  placed  in 
front  of  the  electric  lamp,  and  a  thin  slice  of  the  beam 
is  permitted  to  pass  through  it,  scarcely  any  polarised  light 
is  discharged,  and  scarcely  any  colour  produced  with  a  plate 
of  selenite.  But  if  a  bit  of  soap  be  agitated  in  the  water 
above  the  beam,  the  moment  the  infinitesimal  particles 
reach  the  light  the  liquid  sends  forth  laterally  almost  per- 
fectly polarised  light ;  and  if  the  selenite  be  employed,  vivid 
colours  flash  into  existence.  A  still  more  brilliant  result  is 
obtained  with  mastic  dissolved  in  a  great  excess  of  alcohol. 

The  selenite  rings,  in  fact,  constitute  an  extremely 
delicate  test  as  to  the  quantity  of  individually  invisible 
particles  in  a  liquid.  Commencing  with  distilled  water, 
for  example,  a  thick  slice  of  light  is  necessary  to  make  the 
polarisation  of  its  suspended  particles  sensible.  A  much 
thinner  slice  suffices  for  common  water;  while,  with 
Briicke's  precipitated  mastic,  a  slice  too  thin  to  pro- 
duce any  sensible  effect  with  most  other  liquids,  suffices 
to  bring  out  vividly  the  selenite  colours. 

§  3.    THE  SKY  OF  THE  ALPS. 

The  vision  of  an  object  always  implies  a  differential 
action  on  the  retina  of  the  observer.  The  object  is  dis- 
tinguished from  surrounding  space  by  its  excess  or  de- 
fect of  light  in  relation  to  that  space.  By  altering  the 
illumination,  either  of  the  object  itself  or  of  its  environ- 
ment, we  alter  the  appearance  of  the  object.  Take  the 
case  of  clouds  floating  in  the  atmosphere  with  patches  of 

by  reflection  to  polarisation  by  refraction.  This  thought  repeatedly  occurred 
to  me  while  looking  at  the  effects  ;  but  it  will  require  much  following  up 
before  it  emerges  into  clearness. 


120  FRAGMENTS   OP   SCIENCE. 

blue  between  them.  Anything  that  changes  the  illumina- 
tion of  either  alters  the  appearance  of  both,  that  appear- 
ance depending,  as  stated,  upon  differential  action.  Now 
the  light  of  the  sky,  being  polarised,  may,  as  the  reader 
of  the  foregoing  pages  knows,  be  in  great  part  quenched  by 
a  Nicol's  prism,  while  the  light  of  a  common  cloud,  being 
un  polarised,  cannot  be  thus  extinguished.  Hence  the 
possibility  of  very  remarkable  variations,  not  only  in  the 
aspect  of  the  firmament,  which  is  really  changed,  but  also 
in  the  aspect  of  the  clouds,  which  have  that  firmament 
as  a  blackground.  It  is  possible,  for  example,  to  choose 
clouds  of  such  a  depth  of  shade  that  when  the  Nicol 
quenches  the  light  behind  them,  they  shall  vanish,  being 
undistinguishable  from  the  residual  dull  tint  which  outlives 
the  extinction  of  the  brilliancy  of  the  sky.  A  cloud  less 
deeply  shaded,  but  still  deep  enough,  when  viewed  with 
the  naked  eye,  to  appear  dark  on  a  bright  ground,  is 
suddenly  changed  to  a  white  cloud  on  a  dark  ground 
by  the  quenching  of  the  light  behind  it.  When  a  reddish 
cloud  at  sunset  chances  to  float  in  the  region  of  maxi- 
mum polarisation,  the  quenching  of  the  surrounding  light 
causes  it  to  flash  with  a  brighter  crimson.  Last  Easter 
eve  the  Dartmoor  sky,  which  had  just  been  cleansed  by 
a  snow-storm,  wore  a  very  wild  appearance.  Bound 
the  horizon  it  was  of  steely  brilliancy,  while  reddish 
cumuli  and  cirri  floated  southwards.  When  the  sky 
was  quenched  behind  them  these  floating  masses  seemed 
like  dull  embers  suddenly  blown  upon ;  they  brightened 
like  a  fire.  In  the  Alps  we  have  the  most  magnificent 
examples  of  crimson  clouds  and  snows,  so  that  the  effects 
just  referred  to  may  be  here  studied  under  the  best 
possible  conditions.  On  August  23,  1869,  the  evening 
Alpenglow  was  very  fine,  though  it  did  not  reach  its 
maximum  depth  and  splendour.  The  side  of  the  Weiss- 
horn  seen  from  the  Bel  Alp,  being  turned  from  the 


ARTIFICIAL   SKY.  121 

sun,  was  tinted  mauve;  but  I  wished  to  observe  one 
of  the* rose-coloured  buttresses  of  the  mountain.  Such 
was  visible  from  a  point  a  few  hundred  feet  above  the 
hotel.  The  Matterhorn  also,  though  for  the  most  part  in 
shade,  had  a  crimson  projection,  while  a  deep  ruddy  red 
lingered  along  its  western  shoulder.  Four  distinct  peaks 
and  buttresses  of  the  Dom,  in  addition  to  its  dominant 
head — all  covered  with  pure  snow — were  reddened  by 
the  light  of  sunset.  The  shoulder  of  the  Alphubel  was 
similarly  coloured,  while  the  great  mass  of  the  Fletschorn 
was  all  a-glow,  and  so  was  the  snowy  spine  of  the  Monte 
Leona. 

Looking  at  the  Weisshorn  through  the  Nicol,the  glow  of 
its  protuberance  was  strong  or  weak  according  to  the  posi- 
tion of  the  prism.  The  summit  also  underwent  striking 
changes.  In  one  position  of  the  prism  it  exhibited  a  pale 
white  against  a  dark  background ;  in  the  rectangular 
position  it  was  a  dark  mauve  against  a  light  background. 
The  red  of  the  Matterhorn  changed  in  a  similar  manner ; 
but  the  whole  mountain  also  passed  through  wonderful 
changes  of  definition.  The  air  at  the  time  was  filled 
with  a  silvery  haze,  in  which  the  Matterhorn  almost 
disappeared.  This  could  be  wholly  quenched  by  the 
Nicol,  and  then  the  mountain  sprang  forth  with  astonish- 
ing solidity  and  detachment  from  the  surrounding  air. 
The  changes  of  the  Dom  were  still  more  wonderful.  A 
vast  amount  of  light  could  be  removed  from  the  sky 
behind  it,  for  it  occupied  the  position  of  maximum 
polarisation.  By  a  little  practice  with  the  Nicol  it  was 
easy  to  render  the  extinction  of  the  light,  or  its  restora 
tion,  almost  instantaneous.  When  the  sky  was  quenched, 
the  four  minor  peaks  and  buttresses,  and  the  summit  of 
the  Dom,  together  with  the  shoulder  of  the  Alphubel, 
glowed  as  if  set  suddenly  on  fire.  This  was  immediately 
dimmed  by  turning  the  Nicol  through  an  angle  of  90°. 


122  FRAGMENTS   OF   SCIENCE. 

It  was  not  the  stoppage  of  the  light  of  the  sky  behind 
the  mountains  alone  which  produced  this  startling  effect; 
the  air  between  them  and  me  was  highly  opalescent,  and 
the  quenching  of  this  intermediate  glare  augmented 
remarkably  the  distinctness  of  the  mountains. 

On  the  morning  of  August  24  similar  effects  were  finely 
shown.  At  10  A.M.  all  three  mountains,  the  Dom,  the 
Matterhorn,  and  the  Weisshorn,  were  powerfully  affected 
by  the  Nicol.  But  in  this  instance  also,  the  line  drawn  to 
the  Dom  being  very  nearly  perpendicular  to  the  solar 
beams,  the  effects  on  this  mountain  were  most  striking. 
The  grey  summit  of  the  Matterhorn,  at  the  same  time, 
could  scarcely  be  distinguished  from  the  opalescent 
haze  around  it ;  but  when  the  Nicol  quenched  the 
haze,  the  summit  became  instantly  isolated,  and  stood 
out  in  bold  definition.  It  is  to  be  remembered  that  in 
the  production  of  these  effects  the  only  things  changed 
are  the  sky  behind,  and  the  luminous  haze  in  front  of  the 
mountains;  that  these  are  changed  because  the  light 
emitted  from  the  sky  and  from  the  haze  is  plane  polarised 
light,  and  that  the  light  from  the  snows  and  from  the 
mountains,  being  sensibly  unpolarised,  is  not  directly 
affected  by  the  Nicol.  It  will  also  be  understood  that  it 
is  not  the  interposition  of  the  haze  as  an  opaque  body 
that  renders  the  mountains  indistinct,  but  the  light  of 
the  haze  which  dims  and  bewilders  the  eye,  and  thus 
weakens  the  definition  of  objects  seen  through  it. 

These  results  have  a  direct  bearing  upon  what  artists 
call  '  aerial  perspective.'  As  we  look  from  the  summit  of 
Mont  Blanc,  or  from  a  lower  elevation,  at  the  serried 
crowd  of  peaks,  especially  if  the  mountains  be  darkly 
coloured — covered  with  pines,  for  example — every  peak 
and  ridge  is  separated  from  the  mountains  behind  it  by  a 
thin  blue  haze  which  renders  the  relations  of  the  moun- 
tains as  to  distance  unmistakable.  When  this  haze  is 


ARTIFICIAL   SKY.  123 

regarded  through  the  Nicol  perpendicular  to  the  sun's 
rays,  it  is  in  many  cases  wholly  quenched,  because  the 
light  which  it  emits  in  this  direction  is  wholly  polarised. 
When  this  happens,  aerial  perspective  is  abolished,  and 
mountains  very  differently  distant  appear  to  rise  in  the 
same  vertical  plane.  Close  to  the  Bel  Alp,  for  instance, 
is  the  gorge  of  the  Massa,  and  beyond  the  gorge  is  a  high 
ridge  darkened  by  pines.  This  ridge  may  be  projected 
upon  the  dark  slopes  at  the  opposite  side  of  the  Khone 
valley,  and  between  both  we  have  the  blue  haze  referred 
to,  throwing  the  distant  mountains  far  away.  But  at 
certain  hours  of  the  day  the  haze  may  be  quenched,  and 
then  the  Massa  ridge  and  the  mountains  beyond  the  Ehone 
seem  almost  equally  distant  from  the  eye.  The  one 
appears,  as  it  were,  a  vertical  continuation  of  the  other. 
The  haze  varies  with  the  temperature  and  humidity  of 
the  atmosphere.  At  certain  times  and  places  it  is  almost 
as  blue  as  the  sky  itself;  but  to  see  its  colour,  the  attention 
must  be  withdrawn  from  the  mountains  and  from  the 
trees  which  cover  them.  In  point  of  fact,  the  haze  is  a 
piece  of  more  or  less  perfect  sky ;  it  is  produced  in  the 
same  manner,  and  is  subject  to  the  same  laws,  as  the 
firmament  itself.  We  live  in  the  sky,  not  under  it. 

These  points  were  further  elucidated  by  the  deport- 
ment of  the  selenite  plate,  with  which  the  readers  of  the 
foregoing  pages  are  so  well  acquainted.  On  some  of 
the  sunny  days  of  August  the  haze  in  the  valley  of  the 
Ehone,  as  looked  at  from  the  Bel  Alp,  was  very  remark- 
able. Towards  evening  the  sky  above  the  mountains  op- 
posite to  my  place  of  observation  yielded  a  series  of  the 
most  splendidly-coloured  iris-rings  ;  but  on  lowering  the 
selenite  until  it  had  the  darkness  of  the  pines  at  the 
opposite  side  of  the  Rhone  valley,  instead  of  the  darkness 
of  space,  as  a  background,  the  colours  were  not  much 
diminished  in  brilliancy.  I  should  estimate  the  distance 


124  FKAGMENTS   OF   SCIENCE. 

across  the  valley,  as  the  crow  flies,  to  the  opposite 
mountain,  at  nine  miles ;  so  that  a  body  of  air  of  this 
thickness  can,  under  favourable  circumstances,  produce 
chromatic  effects  of  polarisation  almost  as  vivid  as  those 
produced  by  the  sky  itself. 

Again:  the  light  of  a  landscape,  as  of  most  other 
things,  consists  of  two  parts ;  the  one,  coming  purely 
from  superficial  reflection,  is  always  of  the  same  colour 
as  the  light  which  falls  upon  the  landscape ;  the  other 
part  reaches  us  from  a  certain  depth  within  the  objects 
which  compose  the  landscape,  and  it  is  this  portion 
of  the  total  light  which  gives  these  objects  their  dis- 
tinctive colours.  The  white  light  of  the  sun  enters  all 
substances  to  a  certain  depth,  and  is  partially  ejected  by 
internal  reflection  ;  each  distinct  substance  absorbing  and 
reflecting  the  light,  in  accordance  with  the  laws  of  its  own 
molecular  constitution.  Thus  the  solar  light  is  sifted  by 
the  landscape,  which  appears  in  such  colours  and  vari- 
ations of  colour  as,  after  the  sifting  process,  reach  the 
observer's  eye.  Thus  the  bright  green  of  grass,  or  the 
darker  colour  of  the  pine,  never  comes  to  us  alone, 
but  is  always  mingled  with  an  amount  of  really  foreign 
light  derived  from  superficial  reflection.  A  certain  hard 
brilliancy  is  conferred  upon  the  woods  and  meadows  by 
this  superficially-reflected  light.  Under  certain  circum- 
stances, it  may  be  quenched  by  a  Nicol's  prism,  and  we 
then  obtain  the  true  colour  of  the  grass  and  foliage. 
Trees  and  meadows,  thus  regarded,  exhibit  a  richness  and 
softness  of  tint  which  they  never  show  as  long  as  the 
superficial  light  is  permitted  to  mingle  with  the  true 
interior  emission.  The  needles  of  the  pines  show  this 
effect  very  well,  large-leaved  trees  still  better ;  while  a 
glimmering  field  of  maize  exhibits  the  most  extraordinary 
variations  when  looked  at  through  the  rotating  Nicol. 
Thoughts  and  questions  like  those  here  referred  to 


ARTIFICIAL   SKY.  126 

took  me,  in  August  1869,  to  the  top  of  the  Aletschhorn. 
The  effects  described  in  the  foregoing  paragraphs  were 
for  the  most  part  reproduced  in  the  summit  of  the  moun- 
tain. I  scanned  the  whole  of  the  sky  with  my  Nicol. 
Both  alone,  and  in  conjunction  with  the  selenite,  it  pro- 
nounced the  perpendicular  to  the  solar  beams  to  be  the 
direction  of  maximum  polarisation.  But  at  no  portion 
of  the  firmament  was  the  polarisation  complete.  The 
artificial  sky  produced  in  the  experiments  recorded  in 
the  preceding  pages  could,  in  this  respect,  be  rendered 
more  perfect  than  the  natural  one ;  while  the  gorgeous 
'residual  blue'  which  makes  its  appearance  when  the 
polarisation  of  the  artificial  sky  ceases  to  be  perfect,  was 
strongly  contrasted  with  the  lack-lustre  hue  which,  in 
the  case  of  the  firmament,  outlived  the  extinction  of  the 
brilliancy.  With  certain  substances,  however,  artificially 
treated,  this  dull  residue  may  also  be  obtained. 

All  along  the  arc  from  the  Matterhorn  to  Mont  Blanc 
the  light  of  the  sky  immediately  above  the  mountains  was 
powerfully  acted  upon  by  the  Nicol.  In  some  cases  the 
variations  of  intensity  were  astonishing.  I  have  already 
said  that  a  little  practice  enables  the  observer  to  shift  the 
Nicol  from  one  position  to  another  so  rapidly  as  to  render 
the  alternate  extinction  and  restoration  of  the  light  imme- 
diate. When  this  was  done  along  the  arc  to  which  I 
have  referred,  the  alternations  of  light  and  darkness  re- 
sembled the  play  of  sheet  lightning  behind  the  moun- 
tains. There  was  an  element  of  awe  connected  with  the 
suddenness  with  which  the  mighty  masses,  ranged  along 
the  line  referred  to,  changed  their  aspect  and  definition 
under  the  operation  of  the  prism. 


126  FRAGMENTS   OF  SCIENCE. 


V. 

ON  DUST  AND  DISEASE 

1870. 
Experiments  on  Dusty  Air. 

OLAK  light,  in  passing  through  a  dark  room,  reveala 
its  track  by  illuminating  the  dust  floating  in  the  air. 
'  The  sun,'  says  Daniel  Culverwell,  '  discovers  atomes, 
though  they  be  invisible  by  candle-light,  and  makes  them 
dance  naked  in  his  beams.' 

In  my  researches  on  the  decomposition  of  vapours  by 
light,  I  was  compelled  to  remove  these  'atomes'  and  this 
dust.  It  was  essential  that  the  space  containing  the  vapours 
should  embrace  no  -visible  thing — that  no  substance 
capable  of  scattering  light  in  the  slightest  sensible  degree 
should,  at  the  outset  of  an  experiment,  be  found  in  the  wide 
'  experimental  tube  '  in  which  the  vapour  was  enclosed. 

For  a  long  time  I  was  troubled  by  the  appearance 
there  of  floating  matter,  which,  though  invisible  in  diffuse 
daylight,  was  at  once  revealed  by  a  powerfully  condensed 
beam.  Two  U-tubes  were  placed  in  succession  in  the 
path  of  the  air,  before  it  entered  the  liquid  whose  vapour 
was  to  be  carried  into  the  experimental  tube.  One  of  the 
U-tubes  contained  fragments  of  glass  wetted  with  con- 
centrated sulphuric  acid  ;  the  other,  fragments  of  marble 
wetted  with  a  strong  solution  of  caustic  potash.1  To  my 
astonishment,  the  air  of  the  Eoyal  Institution,  sent 

1  The  apparatus  is  figured  and  described  at  p.  lf>4. 


OX  DUST  AND   DISEASE.  127 

through  these  tubes  at  a  rate  sufficiently  slow  to  dry  it, 
and  to  remove  its  carbonic  acid,  carried  into  the  experi- 
mental tube  a  considerable  amount  of  mechanically  sus- 
pended matter,  which  was  illuminated  when  the  beam 
passed  through  the  tube.  The  effect  was  substantially 
the  same  when  the  air  was  permitted  to  bubble  through 
the  liquid  acid,  and  through  the  solution  of  potash. 

I  tried  to  intercept  this  floating  matter  in  various 
ways;  and  on  October  5,  1868,  prior  to  sending  the  air 
through  the  drying  apparatus,  it  was  carefully  permitted 
to  pass  over  the  tip  of  a  spirit-lamp  flame.  The  floating 
matter  no  longer  appeared,  having  been  burnt  up  by  the 
flame.  It  was  therefore  organic  matter.  I  was  by  no 
means  prepared  for  this  result ;  having  previously  thought 
that  the  dust  of  our  air  was,  in  great  part,  inorganic  and 
non-combustible. ! 

I  had  constructed  a  small  gus-furnace,  now  much  em- 
ployed by  chemists,  containing  a  platinum  tube,  which 
could  be  heated  to  vivid  redness.1  The  tube  contained  a 
roll  of  platinum  gauze,  which,  while  it  permitted  the  air 
to  pass  through  it,  ensured  the  practical  contact  of  the 
dust  with  the  incandescent  metal.  The  air  of  the  labo- 
ratory was  permitted  to  enter  the  experimental  tube, 
sometimes  through  the  cold,  and  sometimes  through  the 
heated,  tube  of  platinum.  In  the  first  column  of  the 


1  According  to  an  analysis  kindly  furnished  to  me  by  Dr.  Percy,  the 
dust  collected  from  the  walls  of  the  British  Museum  contains  fully  50  per 
cent,  of  inorganic  matter.  I  have  every  confidence  in  the  results  of  this 
distinguished  chemist ;  they  show  that  the  floating  dust  of  our  rooms  is,  as 
it  were,  winnowed  from  the  heavier  matter.  As  bearing  directly  upon  this 
point  I  may  quote  the  following  passage  from  Pasteur:  'Mais  ici  se 
pr^sente  une  remarque :  la  poussiere  que  1'on  trouve  a  la  surface  de  tous 
ies  corps  est  soumise  constamment  a  des  courants  d'air,  qui  doivent  soulever 
Bes  particules  Ies  plus  legeres,  au  nombre  desquelles  se  trouvent,  sang 
doute,  de  preference  Ies  corpuscules  organises,  oeufs  ou  spores,  moins 
lourds  generalement  que  Ies  particules  minerales.' 

*  Pasteur  was,  I  believe,  the  first  to  employ  such  a  tube. 


128  FRAGMENTS   OF   SCIENCE. 

following  fragment  of  a  long  table  the  quantity  of  air 
operated  on  is  expressed  by  the  depression  of  the  mercury 
gauge  of  the  air-pump.  In  the  second  column  the  con- 
dition of  the  platinum  tube  is  mentioned,  and  in  the 
third  the  state  of  the  air  in  the  experimental  tube. 

Quantity  of  air  State  of  platinum  tube          State  of  experimental  tube 

15  inches         .         .         Cold         .         .         Full  ot  particles. 
30      „.         .         .         Ked-hot  .         .         Optically  empty. 

The  phrase  l  optically  empty '  shows  that  when  the 
conditions  of  perfect  combustion  were  present,  the  floating 
matter  totally  disappeared. 

In  a  cylindrical  beam,  which  strongly  illuminated  the 
dust  of  the  laboratory,  I  placed  an  ignited  spirit-lamp. 
Mingling  with  the  flame,  and  round  its  rim,  were  seen 
curious  wreaths  of  darkness  resembling  an  intensely  black 
smoke.  On  placing  the  flame  at  some  distance  below  the 
beam,  the  same  dark  masses  stormed  upwards.  They  were 
blacker  than  the  blackest  smoke  ever  seen  issuing  from 
the  funnel  of  a  steamer;  and  their  resemblance  to  smoke 
was  so  perfect  as  to  lead  the  most  practised  observer  to 
conclude  that  the  apparently  pure  flame  of  the  alcohol 
lamp  required  but  a  beam  of  sufficient  intensity  to  reveal 
its  clouds  of  liberated  carbon. 

But  is  the  blackness  smoke?  This  question  presented 
itself  in  a  moment  and  was  thus  answered :  A  red-hot 
poker  was  placed  underneath  the  beam:  from  it  the  black 
wreaths  also  ascended.  A  large  hydrogen  flame  was  next 
employed,  and  it  produced  those  whirling  masses  of  dark- 
ness, far  more  copiously  than  either  the  spirit-flame  or 
poker.  Smoke  was  therefore  out  of  the  question.1 

1  In  none  of  the  public  rooms  of  the  United  States  where  I  had  the 
honour  to  lecture  was  this  experiment  made.  The  organic  dust  was  too 
scanty.  Certain  rooms  in  England — the  Brighton  Pavilion,  for  example — 
also  lack  the  necessary  conditions. 


ON    DUST   AND    DISEASE.  129 

What,  then,  was  the  blackness  ?  It  was  simply  that  of 
stellar  space  ;  that  is  to  say,  blackness  resulting  from  the 
absence  from  the  track  of  the  beam  of  all  matter  compe- 
tent to  scatter  its  light.  When  the  flame  was  piaced 
below  the  beam  the  floating  matter  was  destroyed  in 
situ ;  and  the  air,  freed  from  this  matter,  rose  into  the 
beam,  jostled  aside  the  illuminated  particles,  and  substi- 
tuted for  their  light  the  darkness  due  to  its  own  perfect 
transparency.  Nothing  could  more  forcibly  illustrate  the 
invisibility  of  the  agent  which  renders  all  things  visible. 
The  beam  crossed,  unseen,  the  black  chasm  formed  by  the 
transparent  air,  while,  at  both  sides  of  the  gap,  the  thick- 
strewn  particles  shone  out  like  a  luminous  solid  under  the 
powerful  illumination. 

It  is  not,  however,  necessary  to  burn  the  particles  to 
produce  a  stream  of  darkness.  Without  actual  combustion, 
currents  may  be  generated  which  shall  displace  the  floating 
matter,  and  appear  dark  amid  the  surrounding  brightness. 
I  noticed  this  effect  first  on  placing  a  red-hot  copper  ball 
below  the  beam,  and  permitting  it  to  remain  there  until 
its  temperature  had  fallen  below  that  of  boiling  water. 
The  dark  currents,  though  much  enfeebled,  were  still  pro- 
duced. They  may  also  be  produced  by  a  flask  filled  with 
hot  water. 

To  study  this  effect  a  platinum  wire  was  stretched 
across  the  beam,  the  two  ends  of  the  wire  being  connected 
with  the  two  poles  of  a  voltaic  battery.  To  regulate  the 
strength  of  the  current  a  rheostat  was  placed  in  the  cir- 
cuit. Beginning  with  a  feeble  current  the  temperature 
of  the  wire  was  gradually  augmented ;  but  long  before  it 
reached  the  heat  of  ignition,  a  flat  stream  of  air  rose  from 
it,  which  when  looked  at  edgeways  appeared  darker  and 
sharper  than  one  of  the  blackest  lines  of  Fraunhofer  in 
the  purified  spectrum.  Eight  and  left  of  this  dark  vertical 
band  the  floating  matter  rose  upwards,  bounding  definitely 


130  FRAGMENTS   OF   SCIENCE. 

the  non-luminous  stream  of  air.  What  is  the  explanation? 
Simply  this :  The  hot  wire  rarefied  the  air  in  contact 
•with  it,  but  it  did  not  equally  lighten  the  floating  matter. 
The  oonvecticn  current  of  pure  air  therefore  passed  up- 
wards among  the  inert  particles,  dragging  them  after  it 
right  and  left,  but  forming  between  them  an  impassable 
black  partition.  This  elementary  experiment  enables  us 
to  render  an  account  of  the  dark  currents  produced  by 
bodies  at  a  temperature  below  that  of  combustion. 

But  when  the  platinum  wire  is  intensely  heated,  the 
floating  matter  is  not  only  displaced,  but  destroyed.  I 
stretched  a  wire  about  4  inches  long  through  the  air  of  an 
ordinary  glass  shade  resting  on  cotton-wool,  which  also  sur- 
rounded the  rim.  The  wire  being  raised  to  a  white  heat 
by  an  electric  current,  the  air  expanded,  and  some  of  it 
was  forced  through  the  cotton-wool.  When  the  current 
was  interrupted,  and  the  air  within  the  shade  cooled,  the 
returning  air  did  not  carry  motes  along  with  it,  being  fil- 
tered by  the  wool.  At  the  beginning  of  this  experiment 
the  shade  was  charged  with  floating  matter;  at  the  end  of 
half  an  hour  it  was  optically  empty. 

On  the  wooden  base  of  a  cubical  glass  shade  measuring 
1 1  ^  inches  a  side,  upright  supports  were  fixed,  and  from 
one  support  to  the  other  38  inches  of  platinum  wire  were 
stretched  in  four  parallel  lines.  The  ends  of  the  platinum 
wire  were  soldered  to  two  stout  copper  wires  which  passed 
through  the  base  of  the  shade  and  could  be  connected 
with  a  battery.  As  in  the  last  experiment  the  shade 
rested  upon  cotton-wool.  A  beam  sent  through  the  shade 
revealed  the  suspended  matter.  The  platinum  wire  was 
then  raised  to  whiteness.  In  five  minutes  there  was  a 
sensible  diminution  of  the  matter,  and  in  ten  minutes  it 
was  totally  consumed. 

Oxygen,  hydrogen,  nitrogen,  carbonic  acid,  so  prepared 
as  to  exclude  all  floating  particles,  produce,  when  poured 


ON   DUST   AND   DISEASE.  131 

or  blown  into  the  beam,  the  darkness  of  stellar  space. 
Coal-gas  does  the  same.  An  ordinary  glass  shade,  placed 
in  the  air  with  its  mouth  downwards,  permits  the  track  of 
the  beam  to  be  seen  crossing  it.  When  coal-gas  or  hydro- 
gen is  permitted  to  enter  the  shade  by  a  tube  reaching  to 
its  top,  the  gas  gradually  fills  the  shade  from  above  down- 
wards. As  soon  as  it  occupies  the  space  crossed  by  the 
beam,  the  luminous  track  is  abolished.  Lifting  the 
shade  so  as  to  bring  the  common  boundary  of  gas  and  air 
above  the  beam,  the  track  flashes  forth.  After  the  shade 
is  full,  if  it  be  inverted,  the  pure  gas  passes  upwards  like 
a  black  smoke  among  the  illuminated  particles. 

The  Germ  Theory  of  Contagious  Disease. 

There  is  no  respite  to  our  contact  with  the  floating 
matter  of  the  air  ;  and  the  wonder  is,  not  that  we  should 
suffer  occasionally  from  its  presence,  but  that  so  small  a 
portion  of  it,  and  even  that  but  rarely  diffused  over  large 
areas,  should  appear  to  be  deadly  to  man.  And  what  is 
this  portion  ?  It  was  some  time  ago  the  current  belief 
that  epidemic  diseases  generally  were  propagated  by  a 
kind  of  malaria,  which  consisted  of  organic  matter  in  a 
state  of  motor-decay ;  that  when  such  matter  was  taken 
into  the  body  through  the  lungs,  skin,  or  stomach,  it  had 
the  power  of  spreading  there  the  destroying  process  by 
which  itself  had  been  assailed.  Such  a  power  was  visibly 
exerted  in  the  case  of  yeast.  A  little  leaven  was  seen 
to  leaven  the  whole  lump— a  mere  speck  of  matter,  in 
this  supposed  state  of  decomposition,  being  apparently 
competent  to  propagate  indefinitely  its  own  decay.  Why 
should  not  a  bit  of  rotten  malaria  act  in  a  similar 
manner  within  the  human  frame?  In  1836  a  very  won- 
derful reply  was  given  to  this  question.  In  that  year 
Cagniard  de  la  Tour  discovered  the  yeast-plant,  a  living 


132  FRAGMENTS   OP   SCIENCE. 

organism,  which  when  placed  in  a  proper  medium  feeds, 
grows,  and  reproduces  itself,  and  in  this  way  carries  on 
the  process  which  we  name  fermentation.  By  this  strik- 
ing discovery  fermentation  was  connected  with  organic 
growth. 

Schwann,  of  Berlin,  discovered  the  yeast-plant  inde- 
pendently about  the  same  time;  and  in  February,  1837, 
he  also  announced  the  important  result,  that  when  a 
decoction  of  meat  is  effectually  screened  from  ordinary 
air,  and  supplied  solely  with  calcined  air,  putrefaction 
never  sets  in.  Putrefaction,  therefore,  he  affirmed  to  be 
caused,  not  by  the  air,  but  by  something  which  could  be 
destroyed  by  a  sufficiently  high  temperature.  The  results 
of  Schwann  were  confirmed  by  the  independent  experi- 
ments of  Helmholtz,  Ure,  and  Pasteur,  while  other 
methods,  pursued  by  Schultze,  and  by  Schroeder  and 
Dusch,  led  to  the  same  result.  But  as  regards  fermenta- 
tion, the  minds  of  chemists,  influenced  probably  by  the 
great  authority  of  Gay-Lussac,  fell  back  upon  the  old  no- 
tion of  matter  in  a  state  of  decay.  It  was  not  the  living 
yeast-plant,  but  the  dead  or  dying  parts  of  it,  which,  as- 
sailed by  oxygen,  produced  the  fermentation.  This  notion 
was  finally  exploded  by  Pasteur.  He  proved  the  real 
'  ferments '  to  be  organised  beings  which  find  in  the  re- 
puted ferments  their  necessary  food. 

Side  by  side  with  these  researches  and  discoveries,  and 
fortified  by  them  and  others,  has  run  the  germ,  theory  of 
epidemic  disease.  The  notion  was  expressed  by  Kircher, 
and  favoured  by  Linnaeus,  that  epidemic  diseases  may  be 
due  to  germs  which  float  in  the  atmosphere,  enter  the 
body,  and  produce  disturbance  by  the  development  within 
the  body  of  parasitic  life.  The  strength  of  this  theory 
consists  in  the  perfect  parallelism  of  the  phenomena  of 
contagious  disease  with  those  of  life.  As  a  planted  acorn 
gives  birth  to  an  oak.  competent  to  produce  a  whole  crop 


ON  DUST   AND   DISEASE.  133 

of  acorns,  each  gifted  with  the  power  of  reproducing  its 
parent  tree  ;  and  as  thus  from  a  single  seedling  a  whole 
forest  may  spring ;  so,  it  is  contended,  these  epidemic 
diseases  literally  plant  their  seeds,  grow,  and  shake  abroad 
new  germs,  which,  meeting  in  the  human  body  their  proper 
food  and  temperature,  finally  takes  possession  of  whole 
populations.  There  is  nothing  to  my  knowledge  in  pure 
chemistry  which  resembles  the  power  of  self-multiplica- 
tion possessed  by  the  matter  which  produces  epidemic 
disease.  If  you  sow  wheat  you  do  not  get  barley  ;  if  you 
sow  small-pox  you  do  not  get  scarlet-fever,  but  small-pox 
indefinitely  multiplied,  and  nothing  else.  The  matter  of 
each  contagious  disease  reproduces  itself  as  rigidly  as  if  it 
were  (as  Miss  Nightingale  puts  it)  dog  or  cat. 

Parasitic  Diseases  of  Silkworms.     Pasteur's  Researches. 

It  is  admitted  on  all  hands  that  some  diseases  are  the 
product  of  parasitic  growth.  Both  in  man  and  in  lower 
creatures,  the  existence  of  such  diseases  has  been  demon- 
strated. I  am  enabled  to  lay  before  you  an  account  of 
an  epidemic  of  this  kind,  thoroughly  investigated  and 
successfully  combated  by  M.  Pasteur.  For  fifteen  years  a 
plague  had  raged  among  the  silkworms  of  France.  They 
had  sickened  and  died  in  multitudes,  while  those  that  suc- 
ceeded in  spinning  their  cocoons  furnished  only  a  fraction 
of  the  normal  quantity  of  silk.  In  1853  the  silk  culture 
of  France  produced  a  revenue  of  one  hundred  and  thirty 
millions  of  francs.  During  the  twenty  previous  years  the 
revenue  had  doubled  itself,  and  no  doubt  was  entertained 
as  to  its  further  augmentation.  The  weight  of  the  cocoons 
produced  in  1853  was  26,000,000  kilogrammes;  in  1865 
it  had  fallen  to  4,000,000,  the  fall  entailing,  in  a  single 
year,  a  loss  of  100,000,000  francs. 

The  country  chiefly  smitten  by  this  calamity  happened 
to  be  that  of  the  celebrated  chemist  Dumas,  now  perpetual 


134  FKAGMENTS   OF   SCIENCE. 

secretary  of  the  French  Academy  of  Sciences.  He  turned 
to  his  friend,  colleague,  and  pupil,  Pasteur,  and  besought 
him,  with  an  earnestness  which  the  circumstances  rendered 
almost  personal,  to  undertake  the  investigation  of  the 
malady.  Pasteur  at  this  time  had  never  seen  a  silkworm, 
and  he  urged  his  inexperience  in  reply  to  his  friend. 
But  Dumas  knew  too  well  the  qualities  needed  for  such  an 
enquiry  to  accept  Pasteur's  reason  for  declining  it.  '  Je 
mets,'  said  he,  l  un  prix  extreme  a  voir  votre  attention 
fixee  sur  la  question  qui  interesse  mon  pauvre  pays ;  la 
misere  surpasse  tout  ce  que  vous  pouvez  imaginer.'  Pam- 
phlets about  the  plague  had  been  showered  upon  the 
public,  the  monotony  of  waste  paper  being  broken,  at 
rare  intervals,  by  a  more  or  less  useful  publication.  '  The 
Pharmacopoeia  of  the  Silkworm,'  wrote  M.  Cornalia  in 
1860,  'is  now  as  complicated  as  that  of  man.  Gases, 
liquids,  and  solids  have  been  laid  under  contribution. 
From  chlorine  to  sulphurous  acid,  from  nitric  acid  to  rum, 
from  sugar  to  sulphate  of  quinine, — all  has  been  invoked  in 
behalf  of  this  unhappy  insect.'  The  helpless  cultivators, 
moreover,  welcomed  with  ready  trustfulness  every  new 
remedy,  if  only  pressed  upon  them  with  sufficient  hardi- 
hood. It  seemed  impossible  to  diminish  their  blind 
confidence  in  their  blind  guides.  In  1863  the  French 
Minister  of  Agriculture  signed  an  agreement  to  pay 
500,000  francs  for  the  use  of  a  remedy,  which  its  pro- 
moter declared  to  be  infallible.  It  was  tried  in  twelve 
different  departments  of  France,  and  found  perfectly  use- 
less. In  no  single  instance  was  it  successful.  It  was 
under  these  circumstances  that  M.  Pasteur,  yielding  to 
the  entreaties  of  his  friend,  betook  himself  to  Alais  in  the 
beginning  of  June,  1865.  As  regards  silk  husbandry, 
this  was  the  most  important  department  in  France,  and  it 
was  the  most  sorely  smitten  by  the  plague. 

The  silkworm  had  been  previously  attacked  by  mus- 


ON  DUST  AND   DISEASE.  135 

cardine,  a  disease  proved  by  Bassi  to  be  caused  by  a  vege- 
table parasite.  Though  not  hereditary,  this  malady  was 
propagated  annually  by  the  parasitic  spores.  Wafted  by 
winds  they  often  sowed  the  disease  in  places  far  removed 
from  the  centre  of  infection.  Muscardine  is  now  said  to 
be  very  rare,  a  deadlier  malady  having  taken  its  place.  A 
frequent  outward  sign  of  this  new  disease  are  the  black 
spots  which  cover  the  silkworms ;  hence  the  name  pebrine, 
first  applied  to  the  plague  by  M.  de  Quatrefages,  and 
adopted  by  Pasteur.  Pebrine  declares  itself  in  the  stunted 
and  unequal  growth  of  the  worms,  in  the  languor  of 
their  movements,  in  their  fastidiousness  as  regards  food, 
and  in  their  premature  death.  The  track  of  discovery  as 
regards  the  epidemic  is  this:  In  1849  Gruerin  Meneville 
noticed  in  the  blood  of  silkworms  vibratory  corpuscles, 
which  he  supposed  to  be  endowed  with  independent  life. 
Filippi  proved  him  wrong,  and  showed  that  the  motion  of 
the  corpuscles  was  the  well-known  Brownian  motion.  But 
Filippi  himself  committed  the  error  of  supposing  the  cor- 
puscles to  be  normal  to  the  life  of  the  insect.  They  are 
really  the  cause  of  its  mortality — the  form  and  substance 
of  its  disease.  This  was  well  described  by  Cornalia  ;  while 
Lebert  and  Frey  subsequently  found  the  corpuscles  not 
only  in  the  blood,  but  in  all  the  tissues  of  the  insect. 
Osimo,  in  1857,  discovered  them  in  the  eggs;  and  on  this 
observation  Vittadiani  founded,  in  1859,  a  practical 
method  of  distinguishing  healthy  from  diseased  eggs. 
The  test  often  proved  fallacious,  and  it  was  never  exten- 
sively applied. 

These  living  corpuscles  take  possession  of  the  intestinal 
canal,  and  spread  thence  throughout  the  body  of  the  worm. 
They  fill  the  silk  cavities,  the  stricken  insect  often  going 
automatically  through  the  motions  of  spinning,  without 
any  material  to  work  upon.  Its  organs,  instead  of  being 
filled  with  the  clear  viscous  liquid  of  the  silk,  are  packed 


136  FRAGMENTS   OF   SCIENCE. 

to  distension  by  the  corpuscles.  On  this  feature  of  the 
plague  Pasteur  fixed  his  entire  attention.  The  cycle  of  the 
silkworm's  life  is  briefly  this  :  From  the  fertile  egg  comes 
the  little  worm,  which  grows,  and  casts  its  skin.  This 
process  of  moulting  is  repeated  two  or  three  times  at  sub- 
sequent intervals  during  the  life  of  the  insect.  After  the 
last  moulting  the  worm  climbs  the  brambles  placed  to 
receive  it,  and  spins  among  them  its  cocoon.  It  passes 
thus  into  a  chrysalis ;  the  chrysalis  becomes  a  moth,  and  the 
moth,  when  liberated,  lays  the  eggs  which  form  the  starting- 
point  of  a  new  cycle.  Now  Pasteur  proved  that  the  plague- 
corpuscles  might  be  incipient  in  the  egg,  and  escape  detec- 
tion ;  they  might  also  be  germinal  in  the  worm,  and  still 
baffle  the  microscope.  But  as  the  worm  grows,  the  corpus- 
cles grow  also,  becoming  larger  and  more  defined.  In  the 
aged  chrysalis  they  are  more  pronounced  than  in  the  worm  ; 
while  in  the  moth,  if  either  the  egg  or  the  worm  from 
which  it  comes  should  have  been  at  all  stricken,  the  cor- 
puscles infallibly  appear,  offering  no  difficulty  of  detec- 
tion. This  was  the  first  great  point  made  out  in  1865  by 
Pasteur.  The  Italian  naturalists,  as  aforesaid,  recom- 
mended the  examination  of  the  eggs  before  risking  their 
incubation.  Pasteur  showed  that  both  eggs  and  worms 
might  be  smitten,  and  still  pass  muster,  the  culture  of 
such  eggs  or  such  worms  being  sure  to  entail  disaster.  He 
made  the  moth  his  starting-point  in  seeking  to  regenerate 
the  race. 

Pasteur  made  his  first  communication  on  this  subject 
to  the  Academy  of  Sciences  in  September,  1865.  It  raised 
a  cloud  of  criticism.  Here,  forsooth,  was  a  chemist  rashly 
quitting  his  proper  metier  and  presuming  to  lay  down  the 
law  for  the  physician  and  biologist  on  a  subject  which  was 
eminently  theirs.  '  On  trouva  etrange  que  je  fusse  si 
peu  au  courant  de  la  question ;  on  m'opposa  des  travaux 
qiii  avaient  paru  d°pnis  longtemps  en  Italic,  dont  les 


OX   DUST   AND   DISEASE.  137 

resultats  montraient  1'inutilite  de  mes  efforts,  et  I'impossi- 
bilite  d'arriver  a  un  resultat  pratique  dans  la  direction 
que  je  m'etais  engage.  Que  mon  ignorance  fut  grande 
au  sujet  des  recherches  sans  nombre  qui  avaient  paru  depuis 
quinze  annees.'  Pasteur  heard  the  buzz,  but  he  con- 
tinued his  work.  In  choosing  the  eggs  intended  for  in- 
cubation, the  cultivators  selected  those  produced  in  the 
successful  '  educations '  of  the  year.  But  they  could  not 
understand  the  frequent  and  often  disastrous  failures  of 
their  selected  eggs ;  for  they  did  not  know,  and  nobody 
prior  to  Pasteur  was  competent  to  tell  them,  that  the 
finest  cocoons  may  envelope  doomed  corpusculous  moths. 
It  was  not,  however,  easy  to  make  the  cultivators  accept 
new  guidance.  To  strike  their  imagination,  and  if  pos- 
sible determine  their  practice,  Pasteur  hit  upon  the  ex- 
pedient of  prophecy.  In  1866  he  inspected,  at  St. 
Hippolyte-du-Fort,  fourteen  different  parcels  of  eggs  in- 
tended for  incubation.  Having  examined  a  sufficient 
number  of  the  moths  which  produced  these  eggs,  he 
wrote  out  the  prediction  of  what  would  occur  in  1867,  and 
placed  the  prophecy  as  a  sealed  letter  in  the  hands  of  the 
Mayor  of  St.  Hippolyte. 

In  1867  the  cultivators  communicated  to  the  mayor 
their  results.  The  letter  of  Pasteur  was  then  opened  and 
read,  and  it  was  found  that  in  twelve  out  of  fourteen 
cases  there  was  absolute  conformity  between  his  pre- 
diction and  the  observed  facts.  Many  of  the  groups  had 
perished  totally  ;  the  others  had  perished  almost  totally ; 
and  this  was  the  prediction  of  Pasteur.  In  two  out  of 
the  fourteen  cases,  instead  of  the  prophesied  destruction, 
half  an  average  crop  was  obtained.  Now,  the  parcels  of 
eggs  here  referred  to  were  considered  healthy  by  their 
owners.  They  had  been  hatched  and  tended  in  the  firm 
hope  that  the  labour  expended  on  them  would  prove 
remunerative.  The  application  of  the  moth-test  for  a  few 


138  FRAGMENTS   OP   SCIENCE. 

minutes  in  1866,  would  have  saved  the  labour  and  averted 
the  disappointment.  Two  additional  parcels  of  eggs  were 
at  the  same  time  submitted  to  Pasteur.  He  pronounced 
them  healthy ;  and  his  words  were  verified  by  the  pro- 
duction of  an  excellent  crop.  Other  cases  of  prophecy 
still  more  remarkable,  because  more  circumstantial,  are 
recorded  in  Pasteur's  work. 

Pasteur  subjected  the  development  of  the  corpuscles  to 
a  searching  investigation,  and  followed  out  with  admirable 
skill  and  completeness  the  various  modes  by  which 
the  plague  was  propagated.  From  moths  perfectly  free 
from  corpuscles  he  obtained  healthy  worms,  and  se- 
lecting 10,  20,  30,  50,  as  the  case  might  be,  he  in- 
troduced into  the  worms  the  corpusculous  matter.  It 
was  first  permitted  to  accompany  the  food.  Let  us  take 
a  single  example  out  of  many.  Eubbing  up  a  small 
corpusculous  worm  in  water,  he  smeared  the  mixture 
over  the  mulberry-leaves.  Assuring  himself  that  the 
leaves  had  been  eaten,  he  watched  the  consequences  from 
day  to  day.  Side  by  side  with  the  infected  worms  he 
reared  their  fellows,  keeping  them  as  much  as  possible 
out  of  the  way  of  infection.  These  constituted  his  '  lot 
temoign,' — his  standard  of  comparison.  On  April  16, 
1868,  he  thus  infected  thirty  worms.  Up  to  the  23rd 
they  remained  quite  well.  On  the  25th  they  seemed 
well,  but  on  that  day  corpuscles  were  found  in  the  intes- 
tines of  two  of  them.  On  the  27th,  or  eleven  days  after 
the  infected  repast,  two  fresh  worms  were  examined,  and 
not  only  was  the  intestinal  canal  found  in  each  case  invaded, 
but  the  silk  organ  itself  was  charged  with  corpuscles. 
On  the  28th  the  twenty-six  remaining  worms  were  covered 
by  the  black  spots  of  pebrine.  On  the  30th  the  difference 
of  size  between  the  infected  and  non-infected  worms  was 
very  striking,  the  sick  worms  being  not  more  than  two- 
thirds  of  the  bulk  of  the  healthy  ones.  On  May  2 


ON   DUST   AND   DISEASE.  139 

a  worm  which  had  just  finished  its  fourth  moulting 
was  examined.  Its  whole  body  was  so  filled  with  the 
parasite  as  to  excite  astonishment  that  it  could  live.  The 
disease  advanced,  the  worms  died  and  were  examined, 
and  on  May  11  only  six  out  of  the  thirty  remained. 
They  were  the  strongest  of  the  lot,  but  on  being  searched 
they  also  were  found  charged  with  corpuscles.  Not  one 
of  the  thirty  worms  had  escaped ;  a  single  meal  had 
poisoned  them  all.  The  standard  lot,  on  the  contrary, 
spun  their  fine  cocoons,  two  only  of  their  moths  being 
proved  to  contain  any  trace  of  the  parasite,  which  had 
doubtless  been  introduced  during  the  rearing  of  the 
worms. 

As  his  acquaintance  with  the  subject  increased,  Pas- 
teur's desire  for  precision  augmented,  and  he  finally 
counted  the  growing  number  of  corpuscles  seen  in  the 
field  of  his  microscope  from  day  to  day.  After  a  conta- 
gious repast  the  number  of  worms  containing  the  parasite 
gradually  augmented  until  finally  it  became  cent,  per 
cent.  The  number  of  corpuscles  would  at  the  same  time 
rise  from  0  to  1,  to  10,  to  100,  and  sometimes  even  to 
1,000  or  1,500  in  the  field  of  his  microscope.  He  then 
varied  the  mode  of  infection.  He  inoculated  healthy 
worms  with  the  corpusculous  matter,  and  watched  the 
consequent  growth  of  the  disease.  He  proved  that  the 
worms  inoculate  each  other  by  the  infliction  of  visible 
wounds  with  their  claws.  In  various  cases  he  washed  the 
claws,  and  found  corpuscles  in  the  water.  He  demon- 
strated the  spread  of  infection  by  the  simple  association 
of  healthy  and  diseased  worms.  By  their  claws  and  their 
dejections,  the  diseased  worms  spread  infection.  It  was 
no  hypothetical  infected  medium  —  no  problematical 
pythogenic  gas — that  killed  the  worms,  but  a  definite 
organism.  The  question  of  infection  at  a  distance  was 
also  examined,  and  its  existence  demonstrated.  As  might 


140  FKAGMEXTS   OF   SCIENCE. 

be  expected  from  Pasteur's  antecedents,  the  investigation 
was  exhaustive,  the  skill  and  beauty  of  his  manipulation 
finding  fitting  correlatives  in  the  strength  and  clearness 
of  his  thought. 

The  following  quotation  from  Pasteur's  work  clearly 
shows  the  relation  in  which  his  researches  stand  to  the 
important  question  on  which  he  was  engaged : 

Place  (he  says)  the  most  skilful  educator,  even  the  most 
expert  microscopist,  in  presence  of  large  educations  which  present 
the  symptoms  described  in  our  experiments ;  his  judgment  will 
necessarily  be  erroneous  if  he  confines  himself  to  the  knowledge 
which  preceded  my  researches.  The  worms  will  not  present  to 
him  the  slightest  spot  of  p^brine  ;  the  microscope  will  not  reveal 
the  existence  of  corpuscles;  the  mortality  of  the  worms  will  be 
null  or  insignificant;  and  the  cocoons  leave  nothing  to  be  desired. 
Our  observer  would,  therefore,  conclude  without  hesitation  that 
the  eggs  produced  will  be  good  for  incubation.  The  truth  is,  on 
the  contrary,  that  all  the  worms  of  these  fine  crops  have  been 
poisoned ;  that  from  the  beginning  they  carried  in  them  the  germ 
of  the  malady ;  ready  to  multiply  itself  beyond  measure  in  the 
chrysalides  and  the  moths,  thence  to  pass  into  the  eggs  and  smite 
with  sterility  the  next  generation.  And  what  is  the  first  cause 
of  the  evil  concealed  under  so  deceitful  an  exterior  ?  In  our 
experiments  we  can,  so  to  speak,  touch  it  with  our  fingers.  It  is 
entirely  the  effect  of  a  single  corpusculous  repast;  an  effect  more 
or  less  prompt  according  to  the  epoch  of  life  of  the  worm  that 
has  eaten  the  poisoned  food. 

Pasteur  describes  in  detail  his  method  of  securing 
healthy  eggs.  It  is  nothing  less  than  a  mode  of  restor- 
ing to  France  her  ancient  silk  husbandry.  The  justifica- 
tion of  his  work  is  to  be  found  in  the  reports  which 
reached  him  of  the  application  and  the  unparalleled  suc- 
cess of  his  method,  while  editing  his  researches  for  final 
publication.  In  both  France  and  Italy  his  method  has 
been  pursued  with  the  most  surprising  results.  But  it 
was  an  up-hill  fight  which  led  to  this  triumph.  '  Ever,' 


ON  DUST   AND   DISEASE.  141 

he  say .4,  '  since  the  commencement  of  these  researches,  I 
have  been  exposed  to  the  most  obstinate  and  unjust  con- 
tradictions ;  but  I  have  made  it  a  duty  to  leave  no  trace 
of  these  conflicts  in  this  book.'  And  in  reference  to 
parasitic  diseases,  generally,  he  uses  the  following  weighty 
words :  '  II  est  au  pouvoir  de  I'homme  de  faire  dis- 
paraitre  de  la  surface  du  globe  les  maladies  parasitaires, 
si,  comme  c'est  ma  conviction,  la  doctrine  des  generations 
spontanees  est  une  chimere.' 

Pasteur  dwells  upon  the  ease  with  which  an  island  like 
Corsica  might  be  absolutely  isolated  from  the  silkworm 
epidemic.  And  with  regard  to  other  epidemics,  Mr. 
Simon  describes  an  extraordinary  case  of  insular  exemp- 
tion, for  the  ten  years  extending  from  1851  to  1860.  Of 
the  627  registration  districts  of  England,  one  only  had 
an  entire  escape  from  diseases  which,  in  whole  or  in  part, 
were  prevalent  in  all  the  others :  '  In  all  the  ten  years  it 
had  not  a  single  death  by  measles,  nor  a  single  death  by 
small-pox,  nor  a  single  death  by  scarlet-fever.  And  why  ? 
Not  because  of  its  general  sanitary  merits,  for  it  had  an 
average  amount  of  other  evidence  of  unhealthiness. 
Doubtless,  the  reason  of  its  escape  was  that  it  was  insu- 
lar. It  was  the  district  of  the  Scilly  Isles ;  to  which  it 
was  most  improbable  that  any  febrile  contagion  should 
come  from  without.  And  its  escape  is  an  approximative 
proof  that,  at  least  for  those  ten  years,  no  contagium  of 
measles,  nor  any  contagium  of  scarlet-fever,  nor  any  con- 
tagium of  small-pox  had  arisen  spontaneously  within  its 
limits.'  It  may  be  added  that  there  were  only  seven 
districts  in  England  in  which  no  death  from  diphtheria 
occurred,  and  that,  of  those  seven  districts,  the  district  of 
the  Scilly  Isles  was  one. 

A  second  parasitic  disease  of  silkworms,  called  in  France 
la  flacherie,  co-existent  with  pebrine,  but  quite  distinct 
from  it,  has  also  been  investigated  by  Pasteur.  Enough, 


142  FRAGMENTS   OF   SCIENCE. 

however,  has  been  said  to  send  the  reader  interested  in 
these  questions  to  the  original  volumes  for  further  in- 
formation. To  one  important  practical  point  M.  Pasteur, 
in  a  letter  to  myself,  directs  attention  : 

Permettez-moi  de  terminer  ces  quelques  lignes  que  je  dois 
dieter,  vaincu  que  je  suis  par  la  maladie,  en  vous  faisant  observer 
que  vous  rendriez  service  aux  Colonies  de  la  Grande-Bretagne  en 
repandant  la  connaissance  de  ce  livre,  et  des  principes  que 
j'etablis  touchant  la  maladie  des  vers  a  soie.  Beaucoup  de  ces 
colonies  pourraient  cultiver  le  mftrier  avec  succes,  et  en  jetant 
les  yeux  sur  mon  ouvrage  vous  vous  convaincrez  aisement  qu'il 
est  facile  aujourd'hui,  non-seulement  d'eloigner  la  maladie 
regnante,  mais  en  outre  de  donner  aux  recoltes  de  la  soie  une 
prospdrit£  qu'elles  n'ont  jamais  eue. 

Origin  and  Propagation  of  Contagious  Matter. 
Prior  to  Pasteur,  the  most  diverse  and  contradictory 
opinions  were  entertained  as  to  the  contagious  cha- 
racter of  pebrine;  some  stoutly  affirmed  it,  others  as 
stoutly  denied  it.  But  on  one  point  all  were  agreed. 
*  They  believed  in  the  existence  of  a  deleterious  medium, 
rendered  epidemic  by  some  occult  and  mysterious 
influence,  to  which  was  attributed  the  cause  of  the 
disease.'  Those  acquainted  with  our  medical  literature 
will  not  fail  to  observe  an  instructive  analogy  here. 
We  have  on  the  one  side  accomplished  writers  ascribing 
epidemic  diseases  to  'deleterious  media'  which  arise 
spontaneously  in  crowded  hospitals  and  ill-smelling 
drains.  According  to  them,  the  matter  of  epidemic 
disease  is  formed  de  novo  in  a  putrescent  atmosphere. 
On  the  other  side  we  have  writers,  clear,  vigorous,  with 
well-defined  ideas  and  methods  of  research,  contending 
that  the  matter  which  produces  epidemic  disease  comes 
always  from  a  parent  stock.  It  behaves  as  germinal 
matter,  and  they  do  not  hesitate  to  regard  it  as  such. 
They  no  more  believe  in  the  spontaneous  generation  of 


ON  DUST  AND   DISEASE.  143 

such  diseases,  than  they  do  in  the  spontaneous  generation 
of  mice.  Pasteur,  for  example,  found  that  pebrine  had  been 
known  for  an  indefinite  time  as  a  disease  among  silk- 
worms. The  development  of  it  which  he  combated  was 
merely  the  expansion  of  an  already  existing  power — the 
bursting  into  open  conflagration  of  a  previously  smoul- 
dering fire.  There  is  nothing  surprising  in  this.  For 
though  epidemic  disease  requires  a  special  contagium  to 
produce  it,  surrounding  conditions  must  have  a  potent 
influence  on  its  development.  Common  seeds  may  be 
duly  sown,  but  the  conditions  of  temperature  and  moisture 
may  be  such  as  to  restrict,  or  altogether  prevent,  the 
subsequent  growth.  Looked  at,  therefore,  from  the  point 
of  view  of  the  germ  theory,  the  exceptional  energy  which 
epidemic  disease  from  time  to  time  exhibits,  is  in  har- 
mony with  the  method  of  Nature.  We  sometimes  hear 
diphtheria  spoken  of  as  if  it  were  a  new  disease  of  the 
last  twenty  years ;  but  Mr.  Simon  tells  me  that  about 
three  centuries  ago  tremendous  epidemics  of  it  began  to 
rage  in  Spain  (where  it  was  named  Garrotillo).,  and  soon 
afterwards  in  Italy  ;  and  that  since  that  time  the  disease  has 
been  well  known  to  all  successive  generations  of  doctors. 
In  or  about  1758,  for  instance,  Dr.  Starr,  of  Liskeard,  in 
a  communication  to  the  Eoyal  Society,  particularly 
described  the  disease,  with  all  the  characters  which  have 
recently  again  become  familar,  but  under  the  name  of 
morbus  strangulatorius,  as  then  severely  epidemic  in 
Cornwall.  This  fact  is  the  more  interesting,  as  diph- 
theria, in  its  more  modern  reappearance,  again  showed 
predilection  for  that  remote  county.  Many  also  believe 
that  the  Black  Death,  of  five  centuries  ago,  has  disappeared 
as  mysteriously  as  it  came ;  but  Mr.  Simon  finds  that  it 
is  believed  to  be  prevalent  at  this  hour  in  some  of  the 
north-western  parts  of  India. 

Let  me  here  state  an  item  of  my  own  experience.  When 


144  FRAGMENTS   OF   SCIENCE. 

I  was  at  the  Bel  Alp  last  year  the  English  chaplain 
received  letters  informing  him  of  the  breaking  out  of 
scarlet-fever  among  his  children.  He  lived,  if  I  remember 
rightly,  on  the  healthful  eminence  of  Dartmoor,  and  it 
was  difficult  to  imagine  how  scarlet-fever  could  have  been 
wafted  to  the  place.  A  drain  ran  close  to  his  house,  and 
on  it  his  suspicions  were  manifestly  fixed.  Some  of  our 
medical  writers  would  fortify  him  in  this  notion,  and  thus 
deflect  him  from  the  truth,  while  those  of  another  school 
would  deny  to  a  drain,  however  foul,  the  power  of  pro- 
ducing a  specific  disease.  After  close  enquiry  he  recol- 
lected that  a  hobby-horse  had  been  used  both  by  his  boy 
and  another  who,  a  short  time  previously,  had  passed 
thi  ough  scarlet-fever. 

Drains  and  cesspools,  indeed,  are  by  no  means  in  such 
evil  odour  as  they  used  to  be.  A  fetid  Thames  and  a  low 
death-rate  occur  from  time  to  time  together  in  London. 
For,  if  the  special  matter  or  germs  of  epidemic  disorder 
be  not  present,  a  corrupt  atmosphere,  however  obnoxious 
otherwise,  will  not  produce  the  disorder.  But,  if  the 
germs  be  present,  defective  drains  and  cesspools  become 
the  potent  distributors  of  disease  and  death.  Corrupted 
air  may  promote  an  epidemic,  but  cannot  produce  it.  On 
the  other  hand,  through  the  transport  of  the  special  germ 
or  virus,  disease  may  develop  itself  in  regions  where  the 
drainage  is  good  and  the  atmosphere  pure. 

If  you  see  a  new  thistle  growing  in  your  field  you  feel 
sure  that  its  seed  has  been  wafted  thither.  Just  as  sure 
does  it  seem  that  the  contagious  matter  of  epidemic  dis- 
ease has  been  transplanted  to  the  place  where  it  newly 
appears.  With  a  clearness  and  conclusiveness  not  to  be 
surpassed,  Dr.  William  Budd  has  traced  such  diseases 
from  place  to  place  ;  showing  how  they  plant  themselves, 
at  distinct  foci,  among  populations  subjected  to  the 
same  atmospheric  influences,  just  as  grains  of  corn  might 


ON  DUST  AXD   DISEASED 

J  Aned*t  ca/. 

Le  carried  in  the  pocket  and  sown.  Hildebrand,  to  whose 
remarkable  work,  '  Du  Typhus  contagieux,'  Dr.  de  Mussy 
has  directed  my  attention,  gives  the  following  striking 
case,  both  of  the  durability  and  the  transport  of  the  virus 
of  scarlatina  :  '  Un  habit  noir  que  j'avais  en  visitant  une 
malade  attaquee  de  scarlatine,  et  que  je  portai  de  Vienne 
en  Podolie,  sans  1'avoir  mis  depuis  plus  d'un  an  et  demi, 
me  communiqua,  des  que  je  fus  arrive,  cette  maladie  con- 
tagieuse,  que  je  repandis  ensuite  dans  cette  province,  ou 
elle  etait  jusqu'alors  presque  inconnue.'  Some  years  ago 
Dr.  de  Mussy  himself  was  summoned  to  a  country  house 
in  Surrey,  to  see  a  young  lady  who  was  suffering  from  a 
dropsy,  evidently  the  consequence  of  scarlatina.  The 
original  disease,  being  of  a  very  mild  character,  had  been 
quite  overlooked  ;  but  circumstances  were  recorded  which 
could  leave  no  doubt  upon  the  mind  as  to  the  nature 
and  cause  of  the  complaint.  But  then  the  question  arose, 
How  did  the  young  lady  catch  the  scarlatina  ?  She  had 
come  there  on  a  visit  two  months  previously,  and  it  was 
only  after  she  had  been  a  month  in  the  house  that  she 
was  taken  ill.  The  housekeeper  at  length  cleared  up  the 
mystery.  The  young  lady,  on  her  arrival,  had  expressed  a 
wish  to  occupy  a  room  in  an  isolated  tower.  Her  desire 
was  granted ;  and  in  that  room,  six  months  previously,  a 
visitor  had  been  confined  with  an  attack  of  scarlatina. 
The  room  had  been  swept  and  whitewashed,  but  the 
carpets  had  been  permitted  to  remain. 

Thousands  of  cases  could  probably  be  cited  in  which 
the  disease  has  shown  itself  in  this  mysterious  way,  but 
where  a  strict  examination  has  revealed  its  true  parentage 
and  extraction.  Is  it,  then,  philosophical  to  take  refuge 
in  the  fortuitous  concourse  of  atoms  as  a  cause  of  specific 
disease,  merely  because  in  special  cases  the  parentage 
may  be  indistinct  ?  Those  best  acquainted  with  atomic 
nature,  and  who  are  most  ready  to  admit,  as  regards  even 


140  FRAGMENTS   OP   SCIENCE. 

higher  things  than  this,  the  potentialities  of  matter,  will 
be  the  last  to  accept  these  rash  hypotheses. 

The  Germ,  Theory  applied  to  Surgery. 
Not  only  medical  but  surgical  science  is  now  seeking 
light  and  guidance  from  this  germ  theory.  Upon  it  the 
antiseptic  system  of  Professor  Lister  of  Edinburgh  is 
founded.  As  already  stated,  the  germ  theory  of  putre- 
faction was  started  by  Schwann,  but  the  illustrations  of 
this  theory  adduced  by  Professor  Lister  are  of  such  public 
moment  as  not  only  to  justify,  but  to  render  imperative, 
their  introduction  here. 

Schwann's  observations  (says  Professor  Lister)  did  not  receive 
the  attention  which  they  appeared  to  me  to  have  deserved.  The 
fermentation  of  sugar  was  generally  allowed  to  be  occasioned  by 
the  torula  cerevisice ;  but  it  was  not  admitted  that  putrefaction 
was  due  to  an  analogous  agency.  And  yet  the  two  cases  present 
a  very  striking  parallel.  In  each  a  stable  chemical  compound, 
sugar  in  the  one  case,  albumen  in  the  other,  undergoes  extra- 
ordinary chemical  changes  under  the  influence  of  an  excessively 
minute  quantity  of  a  substance  which,  regarded  chemically,  we 
should  suppose  inert.  As  an  example  of  this  in  the  case  of 
putrefaction,  let  us  take  a  circumstance  often  witnessed  in  the 
treatment  of  large  chronic  abscesses.  In  order  to  guard  against 
the  access  of  atmospheric  air,  we  used  to  draw  off  the  matter  by 
means  of  a  canula  and  trocar,  such  as  you  see  here,  consisting  of 
a  silver  tube  with  a  sharp-pointed  steel  rod  fitted  into  it,  and 
projecting  beyond  it.  The  instrument,  dipped  in  oil,  was  thrust 
into  the  cavity  of  the  abscess,  the  trocar  was  withdrawn,  and  the 
pus  flowed  out  through  the  canula,  care  being  taken  by  gentle 
pressure  over  the  part  to  prevent  the  possibility  of  regurgitation. 
The  canula  was  then  drawn  out  with  due  precaution  against  the 
reflux  of  air.  This  method  was  frequently  successful  as  to  its 
immediate  object,  the  patient  being  relieved  from  the  mass  of 
the  accumulated  fluid,  and  experiencing  no  inconvenience  from 
the  operation.  But  the  pus  was  pretty  certain  to  reaccumulate 
in  course  of  time,  and  it  became  necessary  again  and  again  to 
repeat  the  process.  And  unhappily  there  was  no  absolute 


OX   DUST   AND   DISEASE-  147 

aecurity  of  immunity  from  bad  consequences.  However  care- 
fully the  procedure  was  conducted,  it  sometimes  happened,  even 
though  the  puncture  seemed  healing  by  first  intention,  that 
feverish  symptoms  declared  themselves  in  the  course  of  the  first 
or  second  day,  and,  on  inspecting  the  seat  of  the  abscess,  the 
skin  was  perhaps  seen  to  be  red,  implying  the  presence  of  some 
cause  of  irritation,  while  a  rapid  reaccumulation  of  the  fluid  was 
found  to  have  occurred.  Under  these  circumstances,  it  became 
necessary  to  open  the  abscess  by  free  incision,  when  a  quantity 
large  in  proportion  to  the  size  of  the  abcess,  say,  for  example,  a 
quart,  of  pus  escaped,  fetid  from  putrefaction.  Now,  how  had 
this  change  been  brought  about  ?  Without  the  germ  theory,  I 
venture  to  say,  no  rational  explanation  of  it  could  have  been 
given.  It  must  have  been  caused  by  the  introduction  of  some- 
thing from  without.  Inflammation  of  the  punctured  wound, 
even  supposing  it  to  have  occurred,  would  not  explain  the  pheno- 
menon. For  mere  inflammation,  whether  acute  or  chronic, 
though  it  occasions  the  formation  of  pus,  does  not  induce  putre- 
faction. The  pus  originally  evacuated  was  perfectly  sweet,  and 
we  know  of  nothing  to  account  for  the  alteration  in  its  quality 
but  the  influence  of  something  derived  from  the  external  world. 
And  what  could  that  something  be  ?  The  dipping  of  the  instru- 
ment in  oil,  and  the  subsequent  precautions,  prevented  the  en- 
trance of  oxygen.  Or  even  if  you  allowed  that  a  few  atoms  of 
the  gas  did  enter,  it  would  be  an  extraordinary  assumption  to 
make  that  these  could  in  so  short  a  time  effect  such  changes  in 
so  large  a  mass  of  albuminous  material.  Besides,  the  pyogenic 
membrane  is  abundantly  supplied  with  capillary  vessels,  through 
which  arterial  blood,  rich  in  oxygen,  is  perpetually  flowing ;  and 
there  can  be  little  doubt  that  the  pus,  before  it  was  evacuated  at 
all,  was  liable  to  any  action  which  the  element  might  be  disposed 
to  exert  upon  it. 

On  the  oxygen  theory,  then,  the  occurrence  of  putrefaction 
under  these  circumstances  is  quite  inexplicable.  But  if  you 
admit  the  germ  theory,  the  difficulty  vanishes  at  once.  The 
canula  and  trocar  having  been  lying  exposed  to  the  air,  dust 
will  have  been  deposited  upon  them,  and  will  be  present  in  the 
angle  between  the  trocar  and  the  silver  tube,  and  in  that  pro- 
tected situation  will  fail  to  be  wiped  off  when  the  instrument  is 
*hrust  through  the  tissues.  Then  when  the  trocar  is  withdrawn, 
9 


148  FRAGMENTS   OF   SCIENCE. 

some  portions  of  this  dust  will  naturally  remain  upon  the  margin 
of  the  canula,  which  is  left  projecting  into  the  abscess,  and 
nothing  is  more  likely  than  that  some  particles  may  fail  to  be 
washed  off  by  the  stream  of  out-flowing  pus,  but  may  be  dis- 
lodged when  the  tube  is  taken  out,  and  left  behind  in  the  cavity. 
The  germ  theory  tells  us  that  these  particles  of  dust  will  be 
pretty  sure  to  contain  the  germs  of  putrefactive  organisms,  and 
if  one  such  is  left  in  the  albuminous  liquid,  it  will  rapidly  develop 
at  the  high  temperature  of  the  body,  and  account  for  all  the 
phenomena. 

But  striking  as  is  the  parallel  between  putrefaction  in  this 
instance  and  the  vinous  fermentation,  as  regards  the  greatness  of 
the  effect  produced,  compared  with  the  minuteness  and  the  inert- 
ness, chemically  speaking,  of  the  cause,  you  will  naturally  desire 
further  evidence  of  the  similarity  of  the  two  processes.  You  can 
see  with  the  microscope  the  torula  of  fermenting  must  or  beer. 
Is  there,  you  may  ask,  any  organism  to  be  detected  in  the  putre- 
fying pus  ?  Yes,  gentlemen,  there  is.  If  any  drop  of  the  putrid 
matter  is  examined  with  a  good  glass,  it  is  found  to  be  teeming 
with  myriads  of  minute  jointed  bodies,  called  vibrios,  which 
indubitably  proclaim  their  vitality  by  the  energy  of  their  move- 
ments. It  is  not  an  affair  of  probability,  but  a  fact,  that  the 
entire  mass  of  that  quart  of  pus  has  become  peopled  with  living 
organisms  as  the  result  of  the  introduction  of  the  canula  and 
trocar ;  for  the  matter  first  let  out  was  as  free  from  vibrios  as  it 
was  from  putrefaction.  If  this  be  so,  the  greatness  of  the  chemical 
changes  that  have  taken  place  in  the  pus  ceases  to  be  surprising. 
We  know  that  it  is  one  of  the  chief  peculiarities  of  living  struc- 
tures that  they  possess  extraordinary  powers  of  effecting  chemical 
changes  in  materials  in  their  vicinity,  out  of  all  proportion  to 
their  energy  as  mere  chemical  compounds.  And  we  can  hardly 
doubt  that  the  animalcules  which  have  been  developed  in  the 
albuminous  liquid,  and  have  grown  at  its  expense,  must  have 
altered  its  constitution,  just  as  we  ourselves  alter  that  of  the 
materials  on  which  we  feed.1 

In  the  operations  of  Professor  Lister  care  is  taken 
that  every  portion  of  tissue  laid  bare  by  the  knife  shall 
be  defended  from  germs ;  that  if  they  fall  upon  the 

1  '  Introductory  Lecture  before  the  University  of  Edinburgh.' 


ON  DUST  AND   DISEASE.  149 

wound  they  shall  be  killed  as  they  fall.  With  this  in 
view  he  showers  upon  his  exposed  surfaces  the  spray  of 
diluted  carbolic  acid,  which  is  particularly  deadly  to  the 
germs,  and  he  surrounds  the  wound  in  the  most  careful 
manner  with  antiseptic  bandages.  To  those  accustomed 
to  strict  experiment  it  is  manifest  that  we  have  a  strict 
experimenter  here — a  man  with  a  perfectly  distinct  object 
in  view,  which  he  pursues  with  never-tiring  patience  and 
unwavering  faith.  And  the  result,  in  his  hospital 
practice,  as  described  by  himself,  has  been,  that  even  in 
the  midst  of  abominations  too  shocking  to  be  mentioned 
here,  and  in  the  neighbourhood  of  wards  where  death 
was  rampant  from  pyaemia,  erysipelas,  and  hospital  gan- 
grene, he  was  able  to  keep  his  patients  absolutely  free 
from  these  terrible  scourges.  Let  me  here  recommend 
to  your  attention  Professor  Lister's  'Introductory 
Lecture  before  the  University  of  Edinburgh,'  which  I  have 
already  quoted  ;  his  paper  on  '  The  Effect  of  the  Anti- 
septic System  of  Treatment  on  the  Salubrity  of  a  Surgical 
Hospital ; '  and  the  article  in  the '  British  Medical  Journal ' 
of  January  14,  1871. 

If,  instead  of  using  carbolic  acid  spray,  he  could  sur- 
round his  wounds  with  properly  filtered  air,  the  result 
would,  he  contends,  be  the  same.  In  a  room  where  the 
germs  not  only  float  but  cling  to  clothes  and  walls,  this 
would  be  difficult,  if  not  impossible.  But  surgery  is 
acquainted  with  a  class  of  wounds  in  which  the  blood  is 
freely  mixed  with  air  that  has  passed  through  the  lungs, 
and  it  is  a  most  remarkable  fact  that  such  air  does  not 
produce  putrefaction.  Professor  Lister,  as  far  as  I  know, 
was  the  first  to  give  a  philosophical  interpretation  of  this 
feet,  which  he  describes  and  comments  upon  thus : 

I  have  explained  to  my  own  mind  the  remarkable  fact  that 
in  simple  fracture  of  the  ribs,  if  the  lung  be  punctured  by  a 
fragment,  the  blood  effused  into  the  pleural  cavity,  though 


150  FRAGMENTS   OF   SCIENCE. 

freely  mixed  with  air,  undergoes  no  decomposition.  The  air  ia 
sometimes  pumped  into  the  pleural  cavity  in  such  abundance 
that,  making  its  way  through  the  wound  in  the  pleura  costalis,  it 
inflates  the  cellular  tissue  of  the  whole  body.  Yet  this  occasions 
no  alarm  to  the  surgeon  (although  if  the  blood  in  the  pleura 
were  to  putrefy,  it  would  infallibly  occasion  dangerous  suppu- 
rative  pleurisy).  Why  air  introduced  into  the  pleural  cavity 
through  a  wounded  lung,  should  have  such  wholly  different 
effects  from  that  entering  directly  through  a  wound  in  the  chest, 
was  to  me  a  complete  mystery  until  I  heard  of  the  germ  theory 
of  putrefaction,  when  it  at  once  occurred  to  me  that  it  was  only 
natural  that  air  should  be  filtered  of  germs  by  the  air-passages, 
one  of  whose  offices  is  to  arrest  inhaled  particles  of  dust,  and  pre- 
vent them  from  entering  the  air-cells. 

I  shall  have  occasion  to  refer  to  this  remarkable  hypothesis 
farther  on. 

The  advocates  of  the  germ  theory,  both  of  putrefaction 
and  epidemic  disease,  hold  that  both  arise,  not  from  the 
air,  but  from  something  contained  in  the  air.  They  hold, 
moreover,  that  this  '  something '  is  not  a  vapour  nor  a 
gas,  nor  indeed  a  molecule  of  any  kind,  but  a  particle.1 
The  term  'particulate'  has  been  used  in  the  Keports  of 
the  Medical  Department  of  the  Privy  Council  to  describe 
this  supposed  constitution  of  contagious  matter ;  and  Dr. 
Sanderson's  experiments  render  it  in  the  highest  degree 
probable,  if  they  do  not  actually  demonstrate,  that  the 
virus  of  small-pox  is  '  particulate.'  Definite  knowledge 
upon  this  point  is  of  exceeding  importance,  because  in 
the  treatment  of  particles  methods  are  available  which 
it  would  be  futile  to  apply  to  molecules. 

1  As  regards  size,  there  is  probably  no  sharp  line  of  division  between 
molecules  and  particles  ;  the  one  gradually  shades  into  the  other.  But  the 
distinction  that  I  would  draw  is  this :  the  atom  or  the  molecule,  if  free,  is 
always  part  of  a  gas,  the  particle  is  never  so.  A  particle  is  a  bit  of  liquid 
or  solid  matter,  formed  by  the  aggregation  of  atoms  or  molecules. 


ON  DUST  AND   DISEASE.  16] 


Application  of  Luminous  Beams  to  these  Researches. 

My  own  interference  with  this  great  question,  while 
sanctioned  by  eminent  names,  has  been  also  an  object  of 
varied  and  ingenious  attack.  On  this  point  I  will  only 
say  that  when  angry  feeling  escapes  from  behind  the 
intellect,  where  it  may  be  useful  as  an  urging  force,  and 
places  itself  athwart  the  intellect,  it  is  liable  to  produce 
all  manner  of  delusions.  Thus  my  censors,  for  the  most 
part,  have  levelled  their  remarks  against  positions  which 
were  never  assumed,  and  against  claims  which  were  never 
made.  The  simple  history  of  the  matter  is  this  :  During 
the  autumn  of  1868  I  was  much  occupied  with  the  obser- 
vations referred  to  at  the  beginning  of  this  discourse. 
For  fifteen  years  it  had  been  my  habit  to  make  use  of 
floating  dust  to  reveal  the  paths  of  luminous  beams 
through  the  air;  but  until  1868  I  did  not  intentionally 
reverse  the  process,  and  employ  a  luminous  beam  to  reveal 
and  examine  the  dust.  In  a  paper  presented  to  the  Eoyal 
Society  in  December,  1869,  the  observations  which  in- 
duced me  to  give  more  special  attention  to  the  question 
of  spontaneous  generation,  and  the  germ  theory  of  epi- 
demic disease,  are  thus  described  : 

The  Floating  Matter  of  the  Air. 

Prior  to  the  discovery  of  the  foregoing  action  (the  chemical 
action  of  light  upon  vapours,  Fragment  IV.),  and  also  during 
the  experiments  just  referred  to,  the  nature  of  my  work  compelled 
me  to  aim  at  obtaining  experimental  tubes  absolutely  clean  upon 
the  surface,  and  absolutely  free  within  from  suspended  matter. 
Neither  condition  is,  however,  easily  attained. 

For  however  well  the  tubes  might  be  washed  and  polished, 
and  however  bright  and  pure  they  might  appear  in  ordinary 
daylight,  the  electric  beam  infallibly  revealed  signs  and  tokens 
of  dirt.  The  air  was  always  present,  and  it  was  sure  to  deposit 


152  FRAGMENTS   OF   SCIENCE. 

some  impurity.  All  chemical  processes,  not  conducted  in  a 
vacuum,  are  open  to  this  disturbance.  When  the  experimental 
tube  was  exhausted,  it  exhibited  no  trace  of  floating  matter,  but 
on  admitting  the  air  through  the  U-tubes  (containing  caustic 
potash  and  sulphuric  acid),  a  dust-cone  more  or  less  distinct  was 
always  revealed  by  the  poweifully  condensed  electric  beam. 

The  floating  motes  resembled  minute  particles  of  liquid 
which  had  been  carried  mechanically  from  the  U-tubes  into  the 
experimental  tube.  Precautions  were  therefore  taken  to  prevent 
any  such  transfer.  They  produced  little  or  no  mitigation.  I 
did  not  imagine,  at  the  time,  that  the  dust  of  the  external  air 
could  find  such  free  passage  through  the  caustic  potash  and 
sulphuric  acid.  This,  however,  was  the  case  ;  the  motes  really 
came  from  without.  They  also  passed  with  freedom  through  a 
variety  of  ethers  and  alcohols.  In  fact,  it  requires  long-con- 
tinued action  on  the  part  of  an  acid  first  to  wet  the  motes  and 
afterwards  to  destroy  them.  By  carefully  passing  the  air  through 
the  flame  of  a  spirit-lamp,  or  through  a  platinum  tube  heated  to 
bright  redness,  the  floating  matter  was  sensibly  destroyed.  It 
was  therefore  combustible,  in  other  words,  organic,  matter.  I 
tried  to  intercept  it  by  a  large  respirator  of  cotton-wool.  Close 
pressure  was  necessary  to  render  the  wool  effective.  A  plug  of 
the  wool,  rammed  pretty  tightly  into  the  tube  through  which  the 
air  passed,  was  finally  found  competent  to  hold  back  the  motes. 
They  appeared  from  time  to  time  afterwards,  and  gave  me  much 
trouble ;  but  they  were  invariably  traced  in  the  end  to  some 
defect  in  the  purifying  apparatus — to  some  crack  or  flaw  in  the 
sealing-wax  employed  to  render  the  tubes  air-tight.  Thus 
through  proper  care,  but  not  without  a  great  deal  of  searching 
out  of  disturbances,  the  experimental  tube,  even  when  filled 
with  air  or  vapour,  contains  nothing  competent  to  scatter  the 
light.  The  space  within  it  has  the  aspect  of  an  absolute 
vacuum. 

An  experimental  tube  in  this  condition  I  call  optically 
empty , 

The  simple  apparatus  employed  in  these  experiments  will  be 
at  once  understood  by  reference  to  the  figure  on  page  154.  S  S' 
is  the  glass  experimental  tube,  which  has  varied  in  length  from 
1  to  5  feet,  and  which  may  be  from  2  to  3  inches  in  diameter. 
From  the  end  S,  the  pipe  p  p'  passes  to  an  air-pump.  Connected 


ON   DUST   AND   DISEASE.  163 

with  the  other  end  S'  we  have  the  flask  F,  containing  the  liquid 
•whose  vapour  is  to  be  examined ;  then  follows  a  U-tube,  T, 
filled  with  fragments  of  clean  glass,  wetted  with  sulphuric  acid  ; 
then  a  second  U-tube,  T',  containing  fragments  of  marble,  wetted 
with  caustic  potash  ;  and  finally  a  narrow  straight  tube  t  t',  con- 
taining a  tolerably  tightly  fitting  plug  of  cotton-wool.  To  save 
the  air-pump  gauge  from  the  attack  of  such  vapours  as  act  on 
mercury,  as  also  to  facilitate  observation,  a  separate  barometer 
tube  was  employed. 

Through  the  cork  which  stops  the  flask  F  two  glass  tubes, 
a  and  Z>,  pass  air-tight.  The  tube  a  ends  immediately  under  the 
cork  ;  the  tube  /;,  on  the  contrary,  descends  to  the  bottom  of  the 
flask  and  dips  into  the  liquid.  The  end  of  the  tube  b  is  drawn 
out  so  as  to  render  very  small  the  orifice  through  which  the  air 
escapes  into  the  liquid. 

The  experimental  tube  S  S'  being  exhausted,  a  cock  at  the 
end  S'  is  turned  carefully  on.  The  air  passes  slowly  through 
the  cotton -wool,  the  caustic  potash,  and  the  sulphuric  acid  in 
succession.  Thus  purified,  it  enters  the  flask  F  and  bubbles 
through  the  liquid.  Charged  with  vapour,  it  finally  passes  into 
the  experimental  tube,  where  it  is  submitted  to  examination. 
The  electric  lamp  L  placed  at  the  end  of  the  experimental  tube 
furnishes  the  necessary  beam. 

The  facts  here  forced  upon  my  attention  had  a  bearing 
too  evident  to  be  overlooked.  The  inability  of  air  which 
had  been  filtered  through,  cotton-wool  to  generate  animal- 
cular  life,  had  been  demonstrated  by  Schroeder  and 
Pasteur  :  here,  the  cause  of  its  impotence  was  rendered 
evident  to  the  eye.  The  experiment  proved  that  no 
sensible  amount  of  light  was  scattered  by  the  molecules 
of  the  air ;  that  the  scattered  light  always  arose  from  sus- 
pended particles  ;  and  the  fact  that  the  removal  of  these 
abolished  simultaneously  the  power  of  scattering  light 
and  of  originating  life,  obviously  detached  the  life-origi- 
nating power  from  the  air,  and  fixed  it  on  something  sus- 
pended in  the  air.  Gases  of  all  kinds  passed  with  freedom 
through  the  plug  of  cotton- wool ;  hence  the  tiling  whose 


164 


FEAGMEMS   OF   SCIENCE. 


ON  DUST  AND   DISEASE.  155 

removal  by  the  cotton-wool  rendered  the  gas  impotent, 
could  not  itself  have  been  matter  in  the  gaseous  condition. 
It  at  once  occurred  to  me  that  the  retina,  protected  as  it 
was,  in  these  experiments,  from  all  extraneous  light, 
might  be  converted  into  a  new  and  powerful  instrument 
of  demonstration  in  relation  to  the  germ  theory. 

But  the  observations  also  revealed  the  danger  incurred 
in  experiments  of  this  nature  ;  showing  that  without  an 
amount  of  care  far  beyond  that  hitherto  bestowed  upon 
them,  such  experiments  left  the  door  open  to  errors  of 
the  gravest  description.  It  was  especially  manifest  that 
the  chemical  method  employed  by  Schultz  in  his  experi- 
ments, and  so  often  resorted  to  since,  might  lead  to  the 
most  erroneous  consequences ;  that  neither  acids  nor 
alkalies  had  the  power  of  rapid  destruction  hitherto  as- 
cribed to  them.  In  short,  the  employment  of  the  lumin- 
ous beam  rendered  evident  the  cause  of  success  in  experi- 
ments rigidly  conducted  like  those  of  Pasteur  ;  while  it 
made  equally  evident  the  certainty  of  failure  in  experi- 
ments less  severely  and  less  skilfully  carried  out. 

Dr.  Bennetts  Experiments. 

But  I  do  not  wish  to  leave  an  assertion  of  this  kind 
without  illustration.  Take,  then,  the  well-conceived 
experiments  of  Dr.  Hughes  Bennett,  described  before  the 
Royal  Society  of  Surgeons  in  Edinburgh  on  January  17, 
1868.1  Into  flasks  containing  decoctions  of  liquorice-root, 
hay,  or  tea,  Dr.  Bennett,  by  an  ingenious  method,  forced 
air.  The  air  was  driven  through  two  U-tubes,  the  one 
containing  a  solution  of  caustic  potash,  the  other  sulphuric 
acid.  « All  the  bent  tubes  were  filled  with  fragments  of 
pumice-stone  to  break  up  the  air,  so  as  to  prevent  the 
possibility  of  any  germs  passing  through  in  the  centre  of 
bubbles.'  The  air  also  passed  through  a  Liebig's  bulb 

1  'British  Medical  Journal,'  13,  pt.  ii.  1868. 


156  FRAGMENTS  OF   SCIENCE. 

containing  sulphuric  acid,  and  also  through  a  bulb  con- 
taining gun-cotton. 

It  was  only  natural  for  Dr.  Bennett  to  believe  that  his 
'  bent  tubes '  entirely  cut  off  the  germs.  Previous  to  the 
observations  just  referred  to,  I  also  believed  in  their 
efficacy.  But  these  observations  destroy  any  such  notion. 
The  gun-cotton,  moreover,  will  fail  to  arrest  the  whole  of 
the  floating  matter  unless  it  is  tightly  packed,  and  there 
is  no  indication  in  Dr.  Bennett's  memoir  that  it  was  so 
packed.  On  the  whole,  I  should  infer,  from  the  mere 
inspection  of  Dr.  Bennett's  apparatus,  the  very  result? 
which  he  has  described — a  retardation  of  the  develop- 
ment of  life,  a  total  absence  of  it  in  some  cases,  and  its 
presence  in  others. 

In  his  first  series  of  experiments,  eight  flasks  were  fed 
with  his  sifted  air,  and  five  with  common  air.  In  ten  or 
twelve  days  all  the  five  had  fungi  iu  them ;  whilst  it  re- 
quired from  four  to  nine  months  to  develop  fungi  in  the 
others.  In  one  of  the  eight,  moreover,  even  after  this 
interval  no  fungi  appeared.  In  a  second  series  of  ex- 
periments there  was  a  similar  exception.  In  a  third 
series  the  cork  stoppers  used  in  the  first  and  second 
series  were  abandoned,  and  glass  stoppers  employed. 
Flasks  containing  decoctions  of  tea,  beef,  and  hay  were 
filled  with  common  air,  and  other  flasks  with  sifted  air. 
In  every  one  of  the  former  fungi  appeared  and  in  not 
one  of  the  latter.  These  experiments  simply  ruin  the 
doctrine  that  Dr.  Bennett  finally  espouses. 

In  all  these  negative  cases,  the  prepared  air  was  forced 
into  the  infusion  when  it  was  boiling  hot.  Dr.  Bennett 
made  a  fourth  series  of  experiments,  in  which,  previous  to 
forcing  in  the  air,  he  permitted  the  flasks  to  cool.  Into 
four  bottles  thus  treated  he  forced  prepared  air,  and  after 
a  time  found  fungi  in  all  of  them.  What  is  his  conclu- 
sion ?  Not  that  the  boiling  hot  liquid,  employed  in  his 


ON  DUST   AND   DISEASE.  167 

first  experiments,  had  destroyed  such  germs  as  had  run 
the  gauntlet  of  his  apparatus ;  but  that  air  which,  pre- 
vious to  being  sealed  up,  had  been  exposed  to  a  tempera- 
ture of  212°,  is  too  rare  to  support  life  !  This  conclusion  is 
so  remarkable  that  it  ought  to  be  stated  in  Dr.  Bennett's 
own  words.  '  It  may  be  easily  conceived  that  air  sub- 
jected to  a  boiling  temperature  is  so  expanded  as  scarcely 
to  merit  the  name  of  air,  and  that  it  is  more  or  less  unfit 
for  the  purpose  of  sustaining  animal  or  vegetable  life.' 

Now  numerical  data  are  attainable  here,  and  as  a 
matter  of  fact  I  live  and  flourish  for  a  considerable  por- 
tion of  each  year  in  a  medium  of  less  density  than  that 
which  Dr.  Bennett  describes  as  scarcely  meriting  the  name 
of  air.  The  inhabitants  of  the  higher  Alpine  chalets,  with 
their  flocks  and  herds,  and  the  grasses  which  support  these, 
do  the  same ;  while  the  chamois  rears  its  kids  in  air  rarer 
still.  Insect  life,  moreover,  is  sometimes  exhibited  with 
monstrous  prodigality  at  Alpine  heights. 

In  a  fifth  series  of  experiments  sixteen  bottles  were 
filled  with  infusions.  Into  four  of  them,  while  cold,  or- 
dinary unheated  and  unsifted  air  was  pumped.  In  these 
four  bottles  fungi  were  developed.  Into  four  other  bottles, 
containing  a  boiling  infusion,  ordinary  air  was  also  pumped 
— no  fungi  were  here  developed.  Into  four  other  bottles 
containing  an  infusion  which  had  been  boiled  and  per- 
mitted to  cool,  sifted  air  was  pumped — no  fungi  were 
developed.  Finally,  into  four  bottles  containing  a  boiling 
infusion  sifted  air  was  pumped — no  fungi  were  developed. 
Only,  therefore,  in  the  four  cases  where  the  infusions  were 
cold  infusions,  and  the  air  ordinary  air,  did  fungi  appear. 

Dr.  Bennett  does  not  draw  from  his  experiments  the 
conclusion  to  which  they  so  obviously  point.  On  them, 
on  the  contrary,  he  founds  a  defence  of  the  doctrine  of 
spontaneous  generation,  and  a  general  theory  of  sponta- 
neous development.  So  strongly  was  he  impressed  with 


158  FRAGMENTS   OF   SCIENCE. 

the  idea  that  the  germs  could  not  possibly  pass  through 
his  potash  and  sulphuric  acid  tubes,  that  the  appearance 
of  fungi,  even  in  a  small  minority  of  cases,  where  the  air 
had  been  sent  through  these  tubes,  was  to  him  conclusive 
evidence  of  the  spontaneous  origin  of  such  fungi.  And 
he  accounts  for  the  absence  of  life  in  many  of  his  experi- 
ments by  an  hypothesis  which  will  not  bear  a  moment's 
examination.  But,  knowing  that  organic  particles  may 
pass  unscathed  through  alkalies  and  acids,  the  results  of 
Dr.  Bennett  are  precisely  what  ought  under  the  circum- 
stances to  be  expected.  Indeed,  their  harmony  with  the 
conditions  now  revealed  is  a  proof  of  the  honesty  and 
accuracy  with  which  they  were  executed. 

The  caution  exercised  by  Pasteur  both  in  the  exe- 
cution of  his  experiments,  and  in  the  reasoning  based 
upon  them,  is  perfectly  evident  to  those  who,  through  the 
practice  of  severe  experimental  enquiry,  have  rendered 
themselves  competent  to  judge  of  good  experimental  work. 
He  found  germs  in  the  mercury  used  to  isolate  his  air. 
He  was  never  sure  that  they  did  not  cling  to  the  instru- 
ments he  employed,  or  to  his  own  person.  Thus  when  he 
opened  his  hermetically  sealed  flasks  upon  the  Mer  de 
Glace,  he  had  his  eye  upon  the  file  used  to  detach  the 
drawn-out  necks  of  his  bottles  ;  and  he  was  careful  to  stand 
to  leeward  when  each  flask  was  opened.  Using  these  precau- 
tions, he  found  the  glacier  air  incompetent,  in  nineteen 
cases  out  of  twenty,  to  generate  life ;  while  similar  flasks, 
opened  amid  the  vegetation  of  the  lowlands,  were  soon 
crowded  with  living  things.  M.  Pouchet  repeated  Pas- 
teur's experiments  in  the  Pyrenees,  adopting  the  precau- 
tion of  holding  his  flasks  above  his  head,  and  obtaining 
a  different  result.  Now  great  care  would  be  needed  to 
render  this  procedure  a  real  precaution.  The  luminous 
beam  at  once  shows  us  its  possible  effect.  Let  smoking 
brown  paper  be  placed  at  the  open  mouth  of  a  glass 


ON  DUST  AND   DISEASE.  159 

shade,  so  that  the  smoke  shall  ascend  and  fill  the  shade. 
A  beam  sent  through  the  shade  forms  a  bright  track 
through  the  smoke.  When  the  closed  fist  is  placed  under- 
neath the  shade,  a  vertical  wind  of  surprising  violence, 
considering  the  small  elevation  of  temperature,  rises  from 
the  hand,  displacing  by  comparatively  dark  air  the  illumi- 
nated smoke.  Unless  special  care  were  taken  such  a  wind 
would  rise  from  M.  Pouchet's  body  as  he  held  his  flasks 
above  his  head,  and  thus  the  precaution  of  Pasteur,  of  not 
coming  between  the  wind  and  the  flask,  would  be  annulled. 

Let  me  now  direct  attention  to  another  result  of 
Pasteur,  the  cause  and  significance  of  which  are  at  once 
revealed  by  the  luminous  beam.  He  prepared  twenty-one 
flasks,  each  containing  a  decoction  of  yeast,  filtered  and 
clear.  He  boiled  the  decoction  so  as  to  destroy  what- 
ever germs  it  might  contain,  and,  while  the  space  above 
the  liquid  was  filled  with  pure  steam,  he  sealed  his  flasks 
with  a  blow-pipe.  He  opened  ten  of  them  in  the  deep, 
damp  caves  of  the  Paris  Observatory,  and  eleven  of  them 
in  the  courtyard  of  the  establishment.  Of  the  former, 
one  only  showed  signs  of  life  subsequently.  In  nine  out 
of  the  ten  flasks  no  organisms  of  any  kind  were  deve- 
loped. In  all  the  others  organisms  speedily  appeared. 

Now  here  is  an  experiment  conducted  in  Paris,  on 
which  we  can  throw  obvious  light  in  London.  Causing 
our  luminous  beam  to  pass  through  a  large  flask  filled  with 
the  air  of  this  room,  and  charged  with  its  germs  and  its 
dust,  the  beam  is  seen  crossing  the  flask  from  side  to  side. 
But  here  is  another  similar  flask,  which  cuts  a  clear  gap 
out  of  the  beam.  It  is  filled  with  unfiltered  air,  and  still 
no  trace  of  the  beam  is  visible.  Why  ?  By  pure  accident 
I  stumbled  on  this  flask  in  our  apparatus  room,  where  it  had 
•emained  quiet  for  some  time.  Acting  upon  this  obvious 
suggestion  I  set  aside  three  other  flasks,  filled,  in  the  first 
instance,  with  mote-filled  air.  They  are  now  optically 


160  FRAGMENTS   OF  SCIENCE. 

empty.  Our  former  experiments  proved  that  the  life- 
producing  particles  attach  themselves  to  the  fibres  of 
cotton-wool.  In  the  present  experiment  the  motes  have 
been  brought  by  gentle  air-currents,  established  by  slight 
differences  of  temperature  within  our  closed  vessels,  into 
contact  with  the  interior  surface,  to  which  they  adhere. 
The  air  of  these  flasks  has  deposited  its  dust,  germs  and 
all,  and  is  practically  free  from  suspended  matter. 

I  had  a  chamber  erected,  the  lower  half  of  which  is 
of  wood,  its  upper  half  being  enclosed  by  four  glazed 
window-frames.  It  tapers  to  a  truncated  cone  at  the  top 
It  measures  in  plan  3  ft.  by  2  ft.  6  in.,  and  its  height 
is  5  ft.  10  in.  On  February  6  it  was  closed,  every 
crevice  that  could  admit  dust,  or  cause  displacement  of 
the  air,  being  carefully  pasted  over  with  paper.  The 
electric  beam  at  first  revealed  the  dust  within  the  cham- 
ber as  it  did  in  the  air  of  the  laboratory.  The  chamber 
was  examined  almost  daily  ;  a  perceptible  diminution  of 
the  floating  matter  being  noticed  as  time  advanced.  At 
the  end  of  a  week  the  chamber  was  optically  empty,  exhi- 
biting no  trace  of  matter  competent  to  scatter  the  light. 
Such  must  have  been  the  case  in  the  stagnant  caves  of  the 
Paris  Observatory.  "Were  our  electric  beam  sent  through 
the  air  of  these  caves  its  track  would  be  invisible ;  thus 
showing  the  indissoluble  association  of  the  scattering  of 
light  by  air  and  its  power  to  generate  life. 

I  will  now  turn  to  what  seems  to  me  a  more  interest- 
ing application  of  the  luminous  beam  than  any  hitherto 
described.  My  reference  to  Professor  Lister's  interpretation 
of  the  fact,  that  air  which  has  passed  through  the  lungs 
cannot  produce  putrefaction,  is  fresh  in  your  memories. 
1  Why  air,'  said  he,  '  introduced  into  the  pleural  cavity, 
through  a  wounded  lung,  should  have  such  wholly  different 
effects  from  that  entering  through  a  permanently  open 
wound,  penetrating  from  without,  was  to  me  a  complete 


ON  DUST   AND   DISEASE.  161 

mystery,  till  I  heard  of  the  germ  theory  of  putrefaction, 
when  it  at  once  occurred  to  me  that  it  was  only  natural 
that  the  air  should  be  filtered  of  germs  by  the  air-passages, 
one  of  whose  offices  is  to  arrest  inhaled  particles  of  dust, 
and  prevent  them  from  entering  the  air-cells.' 

Here  is  a  surmise  which  bears  the  stamp  of  genius,  but 
which  needs  verification.  If,  for  the  words  '  it  is  only 
natural '  we  were  authorised  to  write  '  it  is  perfectly  cer- 
tain,' the  demonstration  would  be  complete.  Such  de- 
monstration is  furnished  by  experiments  with  a  beam  of 
light.  One  evening,  towards  the  close  of  1869,  while 
pouring  various  pure  gases  across  the  dusty  track  of  a 
luminous  beam,  the  thought  occurred  to  me  of  using  my 
breath  instead  of  the  gases.  I  then  noticed,  for  the  first 
time,  the  extraordinary  darkness  produced  by  the  expired 
air,  towards  the  end  of  the  expiration.  Permit  me  to  re- 
peat the  experiment  in  your  presence.  I  fill  my  lungs  with 
ordinary  air  and  breathe  through  a  glass  tube  across  the 
beam.  The  condensation  of  the  aqueous  vapour  of  the 
breath  is  shown  by  the  formation  of  a  luminous  white  cloud 
of  delicate  texture.  We  abolish  this  cloud  by  drying  the 
breath  previous  to  its  entering  the  beam ;  or,  still  more 
simply,  by  warming  the  glass  tube.  The  luminous  track  of 
the  beam  is  for  a  time  uninterrupted  by  the  breath,  "because 
the  dust  returning  from  the  lungs  makes  good,  in  great 
part,  the  particles  displaced.  After  a  time,  however,  an 
obscure  disk  appears  in  the  beam,  the  darkness  of  which 
increases,  until  finally,  towards  the  end  of  the  expiration, 
the  beam  is,  as  it  were,  pierced  by  an  intensely  black 
hole,  in  which  no  particles  whatever  can  be  discerned. 
The  deeper  air  of  the  lungs  is  thus  proved  to  be  absolutely 
free  from  suspended  matter.  It  is  therefore  in  the  precise 
condition  required  by  Professor  Lister's  explanation. 
This  experiment  may  be  repeated  any  number  of  times 
with  the  same  result.  I  think  it  must  be  regarded  as  a 


FRAGMENTS   OF   SCIENCE. 


crowning  piece  of  evidence  both  of  the  correctness  of 
Professor  Lister's  views  and  of  the  impotence,  as  regards 
vital  development,  of  optically  pure  air.1 


Application  of  Luminous  Beams  to  Water. 

The  method  of  examination  here  pursued  is  also  appli- 
cable to  water.  It  is  in  some  sense  complementary  to 
that  of  the  microscope,  and  may,  I  think,  materially  aid 
enquiries  conducted  with  that  instrument.  In  micro- 
scopic examination  attention  is  directed  to  a  small  portion 
of  the  liquid,  and  the  aim  is  to  detect  the  individual 
suspended  particles.  By  the  present  method  a  large 
portion  of  the  liquid  is  illuminated,  its  general  condition 
being  revealed,  by  the  scattered  light.  Care  is  taken 
to  defend  the  eye  from  the  access  of  all  other  light,  and, 
thus  defended,  it  becomes  an  organ  of  inconceivable  deli- 
cacy. Indeed,  an  amount  of  impurity  so  infinitesimal  as 
to  be  scarcely  expressible  in  numbers,  and  the  individual 
particles  of  which  are  so  small  as  wholly  to  elude  the 
microscope,  may,  when  examined  by  the  method  alluded 
to,  produce  not  only  sensible,  but  striking,  effects  upon 
the  eye. 

We  will  apply  the  method,  in  the  first  place,  to  an 
experiment  of  M.  Pouchet  intended  to  prove  conclusively 
that  animalcular  life  is  developed  in  cases  where  no  ante- 
cedent germs  could  possibly  exist.  He  produced  water 
from  the  combustion  of  hydrogen  in  air,  justly  arguing 
that  no  germ  could  survive  the  heat  of  a  hydrogen 
flame.  But  he  overlooked  the  fact  that  his  aqueous  vapour 
was  condensed  in  the  air,  and  was  allowed  as  water  to 

1  Dr.  Burden  Sanderson  draws  attention  to  the  important  observation 
of  Brauell,  which  shows  that  the  contagium  of  a  pregnant  animal,  suffering 
from  splenic  fever,  is  not  found  in  the  blood  of  the  fcetus ;  the  placental 
apparatus  acting  as  a  filter,  and  holding  back  the  infective  particles. 


ON  DUST  AND   DISEASE.  103 

trickle  through  the  air.  Indeed  the  experiment  is  one  of 
a  number  by  which  workers  like  M.  Pouchet  are  differen- 
tiated from  workers  like  Pasteur.  I  will  show  you  some 
water,  produced  by  allowing  a  hydrogen  flame  to  play 
upon  a  polished  silver  condenser,  formed  by  the  bottom  of 
a  silver  basin,  containing  ice.  The  collected  liquid  is 
pellucid  in  the  common  light;  but  in  the  condensed 
electric  beam  it  is  seen  to  be  laden  with  particles,  so  thick- 
strewn  and  minute  as  to  produce  a  continuous  luminous 
cone.  In  passing  through  the  air  the  water  loaded  itself 
with  this  matter;  and  the  deportment  of  such  water 
could  obviously  have  no  influence  in  deciding  this  great 
question. 

We  are  invaded  with  dirt  not  only  in  the  air  we 
breathe,  but  in  the  water  we  drink.  To  prove  this  I  take 
the  bottle  of  water  intended  to  quench  your  lecturer's 
thirst ;  which,  in  the  track  of  the  beam,  simply  reveals 
itself  as  dirty  water.  And  this  water  is  no  worse  than 
the  other  London  waters.  Thanks  to  the  kindness  of 
Professor  Frankland,  I  have  been  furnished  with  speci- 
mens of  the  water  of  eight  London  companies.  They  are 
all  laden  with  impurities  mechanically  suspended.  But 
you  will  ask  whether  filtering  will  not  remove  the  sus- 
pended matter  ?  The  grosser  matter,  undoubtedly,  but 
not  the  more  finely  divided  matter.  Water  may  be 
passed  any  number  of  times  through  bibulous  paper,  it 
will  continue  laden  with  fine  matter.  Water  passed 
through  the  charcoal  filter  of  Lipscomb's,  or  through  the 
filters  of  the  Silicated  Carbon  Company,  has  its  grosser 
matter  removed,  but  it  is  thick  with  fine  matter.  Nine- 
tenths  of  the  light  scattered  by  these  suspended  particles 
is  perfectly  polarised  in  a  direction  at  right  angles  to  the 
beam,  and  this  release  of  the  particles  from  the  ordinary 
law  of  polarisation  is  a  demonstration  of  their  smallness. 
I  should  say  by  far  the  greater  number  of  the  particles 


164  FRAGMENTS    OF   SCIENCE. 

concerned  in  this  scattering  are  wholly  beyond  the  range 
of  the  microscope,  and  no  ordinary  filter  can  intercept 
such  particles.  It  is  next  to  impossible,  by  artificial 
means,  to  produce  a  pure  water.  Mr.  Hartley,  for  exam- 
ple, some  time  ago  distilled  water  while  it  was  surrounded 
by  hydrogen,  but  the  water  was  not  free  from  floating 
matter.  It  is  so  hard  to  be  clean  in  the  midst  of  dirt. 
In  water  from  the  Lake  of  Geneva,  which  has  remained 
long  without  being  stirred,  we  have  an  approach  to  the 
pure  liquid.  I  have  a  bottle  of  it  here,  which  was  carefully 
filled  for  me  by  my  distinguished  friend  Soret.  The 
track  of  the  beam  through  it  is  of  a  delicate  sky-blue ; 
there  is  scarcely  a  trace  of  grosser  matter. 

The  purest  water  that  I  have  seen — probably  the  purest 
which  has  been  seen  hitherto — has  been  obtained  from  the 
fusion  of  selected  specimens  of  ice.  But  extraordinary  pre- 
cautions are  required  to  obtain  this  degree  of  purity. 
The  following  apparatus  has  been  devised  and  constructed 
by  my  assistant  for  this  purpose :  Through  the  plate  of 
an  air-pump  passes  the  shank  of  a  large  funnel,  attached 
to  which  below  the  plate  is  a  clean  glass  bulb.  In  the 
funnel  is  placed  a  block  of  the  most  transparent  ice,  and 
over  the  funnel  a  glass  receiver.  This  is  first  exhausted 
and  refilled  several  times  with  air,  filtered  by  its  passage 
through  cotton-wool,  the  ice  being  thus  surrounded  by 
pure  moteless  air.  But  the  ice  has  previously  been  in 
contact  with  mote-filled  air ;  it  is  therefore  necessary  to 
let  it  wash  its  own  surface,  and  also  to  wash  the  bulb 
which  is  to  receive  the  water  of  liquefaction.  The  ice  is 
permitted  to  melt,  the  bulb  is  filled  and  emptied  several 
times,  until  finally  the  large  block  dwindles  to  a  small 
one.  We  may  be  sure  that  all  impurity  has  been  thus 
removed  from  the  surface  of  the  ice.  The  water  obtained 
in  this  way  is  the  purest  hitherto  obtained.  Still  I 
should  hesitate  to  call  it  absolutely  pure.  When 


ON  DUST  AND   DISEASE.  165 

condensed  light  is  sent  through  it,  the  track  of  the  beam 
is  not  invisible,  but  of  the  most  exquisitely  delicate  blue. 
This  blue  is  purer  than  that  of  the  sky,  so  that  the  matter 
which  produces  it  must  be  finer  than  that  of  the  sky.  It 
may  be,  and  indeed  has  been,  contended  that  this  blue 
is  scattered  by  the  very  molecules  of  the  water,  and  not  by 
matter  suspended  in  the  water.  But  when  we  remember 
that  this  perfection  of  blue  is  approached  gradually 
through  stages  of  less  perfect  blue  ;  and  when  we  con- 
sider that  a  blue  in  all  respects  similar  is  demonstrably 
obtainable  from  particles  mechanically  suspended,  we 
should  hesitate,  I  think,  to  conclude  that  we  have  arrived 
here  at  the  last  stage  of  purification.  The  evidence,  I 
think,  points  distinctly  to  the  conclusion  that  could  we 
push  the  process  of  purification  still  farther,  even  this 
last  delicate  trace  of  blue  would  disappear. 

Chalk-water.     Clark's  Softening  Process. 

But  is  it  not  possible  to  match  the  water  of  the  Lake 
of  Geneva  here  in  England  ?  Undoubtedly  it  is.  "We 
have  in  England  a  kind  of  rock  which  constitutes  at  once 
an  exceedingly  clean  recipient  and  a  natural  filter,  and 
from  which  we  can  obtain  water  extremely  free  from  me- 
chanical impurities.  I  refer  to  the  chalk  formation,  in 
which  large  quantities  of  water  are  held  in  store.  Our 
chalk  hills  are  in  most  cases  covered  with  thin  layers  of 
soil,  and  with  very  scanty  vegetation.  Neither  opposes 
much  obstacle  to  the  entry  of  the  rain  into  the  chalk, 
where  any  organic  impurity  which  the  water  may  carry 
in  is  soon  oxidised  and  rendered  harmless.  Those  who 
have  scampered  like  myself  over  the  downs  of  Hants  and 
Wilts  will  remember  the  scarcity  of  water  in  these  regions. 
In  fact,  the  rainfall,  instead  of  washing  the  surface  and 
collecting  in  streams,  sinks  into  the  fissured  chalk  and 


IG6  FRAGMENTS   OF   SCIENCE. 

percolates  through  it.  When  this  formation  is  suitably 
tapped,  we  obtain  water  of  exceeding  briskness  and 
purity.  A  large  glass  globe,  filled  with  the  water  of  a 
well  near  Tring  shows  itself  to  be  wonderfully  free 
from  mechanical  impurity.  Indeed,  it  stands  to  reason 
that  water  wholly  withdrawn  from  surface  contamination, 
and  percolating  through  so  clean  a  substance,  should  be 
pure.  It  has  been  a  subject  much  debated,  whether  the 
supply  of  excellent  water  which  the  chalk  holds  in  store 
could  not  be  rendered  available  for  London.  Many  of 
the  most  eminent  engineers  and  chemists  have  ardently 
recommended  this  source,  and  have  sought  to  show,  not 
only  that  its  purity  is  unrivalled,  but  that  its  quantity  is 
practically  inexhaustible.  Data  sufficient  to  test  this  are 
now,  I  believe,  in  existence  ;  the  number  of  wells  sunk  in 
the  chalk  being  so  considerable,  and  the  quantity  of  water 
which  they  yield  so  well  known. 

But  this  water,  so  admirable  as  regards  freedom  from 
mechanical  impurity,  labours  under  the  disadvantage  of 
being  rendered  very  hard  by  the  carbonate  of  lime  which 
it  holds  in  solution.  The  chalk-water  in  the  neighbour- 
hood of  Watford  contains  about  seventeen  grains  of  car- 
bonate of  lime  per  gallon.  This,  in  the  old  terminology, 
used  to  be  called  seventeen  degrees  of  hardness.  Now 
this  hard  water  is  bad  for  tea,  bad  for  washing  ;  and  it  furs 
our  boilers,  because  the  lime  held  in  solution  is  precipi- 
tated by  boiling.  If  the  water  be  used  cold,  its  hardness 
must  be  neutralised  at  the  expense  of  soap,  before  it  will 
give  a  lather.  These  are  serious  objections  to  the  use  of 
chalk-water  in  London.  But  they  are  successfully  met  by 
the  demonstration  that  such  water  can  be  softened  inexpen- 
sively, and  on  a  grand  scale.  I  had  long  known  the  method 
of  softening  water  called  Clark's  process,  but  not  until 
recently,  under  the  guidance  of  Mr.  Homersham,  did  I 
see  proof  of  its  larger  applications.  The  chalk-water  is 


ON  LUST  AND   DISEASE.  167 

softened  for  the  supply  of  the  city  of  Canterbury  ;  and  at 
the  Chiltern  Hills  it  is  softened  for  the  supply  of  Tring 
and  Aylesbury.  Caterham  also  enjoys  the  luxury. 

I  have  visited  all  these  places,  and  made  myself 
acquainted  with  the  works.  At  Canterbury  there  are 
three  reservoirs  covered  in  and  protected,  by  a  concrete 
roof  and  layers  of  pebbles,  both  from  the  summers  heat 
and  the  winter's  cold.  Each  reservoir  can  hold  120,000 
gallons  of  water.  Adjacent  to  these  reservoirs  are  others 
containing  pure  slaked  lime — the  so-called  '  cream  of 
lime.'  These  being  filled  with  water,  the  lime  and  water 
are  thoroughly  mixed  by  air  forced  in  by  an  engine 
through  apertures  in  the  bottom  of  the  reservoir.  The 
water  soon  dissolves  all  the  lime  it  is  capable  of  dis- 
solving. The  mechanically  suspended  lime  is  then  allowed 
to  subside  to  the  bottom,  leaving  a  perfectly  transparent 
lime-water  behind. 

The  softening  process  is  this  :  Into  one  of  the 
empty  reservoirs  is  introduced  a  certain  quantity  of  the 
clear  lime-water,  and  after  this  about  nine  times  the 
quantity  of  the  chalk- water.  The  transparency  imme- 
diately disappears — the  mixture  of  the  two  clear  liquids 
becoming  thickly  turbid,  through  the  precipitation  of 
carbonate  of  lime.  The  precipitate  is  permitted  to  sub- 
side. It  is  crystalline  and  heavy,  and  in  about  twelve 
hours  a  layer  of  pure  white  carbonate  of  lime  is  formed 
at  the  bottom  of  the  reservoir,  with  a  water  of  extra- 
ordinary beauty  and  purity  overhead.  A  few  days  ago 
I  pitched  some  halfpence  into  a  reservoir  sixteen  feet 
deep  at  the  Chiltern  Hills.  This  depth  hardly  dimmed 
the  coin.  Had  I  cast  in  a  pin,  it  could  have  been  seen  at 
the  bottom.  By  this  process  of  softening,  the  water  is 
reduced  from  about  seventeen  degrees  of  hardness,  to 
three  degrees  of  hardness.  It  yields  a  lather  immediately. 
Its  temperature  is  constant  throughout  the  year.  In  the 


168  FKAGMENTS   OF   SCIENCE. 

hottest  summer  it  is  cool,  its  temperature  being  twenty 
degrees  above  the  freezing  point ;  and  it  does  not  freeze 
in  winter  if  conveyed  in  proper  pipes.  The  reservoirs 
are  covered  ;  a  leaf  cannot  blow  into  them,  and  no  surface 
contamination  can  reach  the  water.  It  passes  direct  from 
the  main  into  the  house  tap ;  no  cisterns  are  employed, 
and  the  supply  is  always  fresh  and  pure.  This  is  the 
kind  of  water  which  is  supplied  to  the  fortunate  people  of 
Tring,  Caterham,  and  Canterbury. 

The  foregoing  article,  as  far  as  it  relates  to  the  theory 
which  ascribes  epidemic  disease  to  the  development  of 
low  parasitic  life  within  the  human  life,  was  embodied  in 
a  discourse  delivered  before  the  Eoyal  Institution  in 
January  1870.  In  June  1871,  after  a  brief  reference  to 
the  polarisation  of  light  by  cloudy  matter,  I  ventured 
to  recur  to  the  subject  in  these  terms:  What  is  the 
practical  uses  of  these  curiosities  ?  If  we  exclude  the 
interest  attached  to  the  observation  of  new  facts,  and  the 
enhancement  of  that  interest  through  the  knowledge  that 
facts  often  become  the  exponents  of  laws,  these  curiosities 
are-  in  themselves  worth  little.  They  will  not  enable  us 
to  add  to  our  stock  of  food,  or  drink,  or  clothe?,  or  jewel- 
lery. But  though  thus  shorn  of  all  usefulness  in  them- 
selves, they  may,  by  carrying  thought  into  places  which  it 
would  not  otherwise  have  entered,  become  the  antecedents 
of  practical  consequences.  In  looking,  for  example,  at 
our  illuminated  dust,  we  may  ask  ourselves  what  it  is. 
How  does  it  act,  not  upon  a  beam  of  light,  but  upon  our 
own  organisations  ?  The  question  then  assumes  a  prac- 
tical character.  We  find  on  examination  that  this  dust 
is  organic  matter — in  part  living,  in  part  dead.  There 
are  among  it  particles  of  ground  straw,  torn  rags,  smoke, 
the  pollen  of  flowers,  the  spores  of  fungi,  and  the  germs 
of  other  things.  But  what  have  they  to  do  with  the 


OX  DUST  AM)   DISEASE.  16£ 

animal  economy  ?  Let  me  give  you  an  illustration  to 
which  my  attention  has  been  lately  drawn  by  Mr.  George 
Henry  Lewes,  who  writes  to  me  thus : 

*  I  wish  to  direct  your  attention  to  the  experiments  of 
Von  Eecklingshausen  should  you  happen  not  to  know 
them.  They  are  striking  confirmations  of  what  you  say 
of  dust  and  disease.  Last  spring,  when  I  was  at  his 
laboratory  in  Wiirzburg,  I  examined  with  him  blood  that 
had  been  three  weeks,  a  month,  and  five  weeks,  out  of 
the  body,  preserved  in  little  porcelain  cups  under  glass 
shades.  This  blood  was  living  and  growing.  Not  only 
were  the  Amoeba-like  movements  of  the  white  corpuscles 
present,  but  there  were  abundant  evidences  of  the  growth 
and  development  of  the  corpuscles.  I  also  saw  a  frog's 
heart  still  pulsating  which  had  been  removed  from  the 
body  (I  forget  how  many  days,  but  certainly  more  than  a 
week).  There  were  other  examples  of  the  same  persistent 
vitality,  or  absence  of  putrefaction.  Von  Kecklings- 
hausen  did  not  attribute  this  to  the  absence  of  germs — 
germs  were  not  mentioned  by  him ;  but  when  I  asked  him 
how  he  represented  the  thing  to  himself,  he  said  the  whole 
mystery  of  his  operation  consisted  in  keeping  the  blood 
free  from  dirt.  The  instruments  employed  were  raised  to 
a  red  heat  just  before  use ;  the  thread  was  silver  thread  and 
was  similarly  treated ;  and  the  porcelain  cups,  though  not 
kept  free  from  air,  were  kept  free  from  currents.  He  said  he 
often  had  failures,  and  these  he  attributed  to  particles  of 
dust  having  escaped  his  precautions.' 

Professor  Lister,  who  has  founded  upon  the  removal 
or  destruction  of  this  '  dirt'  great  and  numerous  improve- 
ments in  surgery,  tells  us  the  effect  of  its  introduction  into 
the  blood  of  wounds.  He  informs  us  what  would  happen 
with  the  extracted  blood  should  the  dust  get  at  it.  The 
blood  would  putrefy  and  become  fetid  ;  and  when  you 
examine  more  closely  what  putrefaction  means,  you  find 


170  FRAGMENTS   OF   SCIENCE. 

the  putrefying  substance  swarming  with  organic  life,  the 
germs  of  which  have  been  derived  from  the  air. 

"We  are  now  assuredly  in  the  midst  of  practical  matters  ; 
and  with  your  permission  I  will  refer  once  more  to  a  ques- 
tion which  has  recently  occupied  a  good  deal  of  public 
attention.  As  regards  the  lowest  forms  of  life,  the  world 
is  divided,  and  has  for  a  long  time  been  divided,  into  two 
parties,  the  one  affirming  that  we  have  only  to  submit 
absolutely  dead  matter  to  certain  physical  conditions,  to 
envolve  from  it  living  things  ;  the  other  (without  wishing 
to  set  bounds  to  the  power  of  matter)  affirming  that,  in 
our  day,  life  has  never  been  found  to  rise  independently 
of  pre-existing  life.  I  belong  to  the  party  which  claims 
life  as  a  derivative  of  life.  The  question  has  two  factors — 
the  evidence,  and  the  mind  that  judges  of  the  evidence  ; 
and  it  may  be  purely  a  mental  set  or  bias  on  my  part 
that  causes  me  throughout  this  long  discussion,  to  see,  on 
the  one  side,  dubious  facts  and  defective  logic,  and  on  the 
other  side  firm  reasoning  and  a  knowledge  of  what  rigid 
experimental  enquiry  demands.  But,  judged  of  practically, 
what,  again,  has  the  question  of  Spontaneous  Generation 
to  do  with  us  ?  Let  us  see.  There  are  numerous  diseases 
of  men  and  animals  that  are  demonstrably  the  products  of 
parasitic  life,  and  such  diseases  may  take  the  most  terrible 
epidemic  forms,  as  in  the  case  of  the  silkworms  of  France 
in  our  day.  Now  it  is  in  the  highest  degree  important 
to  know  whether  the  parasites  in  question  are  sponta- 
neously developed,  or  are  wafted  from  without  to  those 
afflicted  with  the  disease.  The  means  of  prevention,  if 
not  of  cure,  would  be  widely  different  in  the  two  cases. 

But  this  is  not  all.  Besides  these  universally  admitted 
cases,  there  is  the  broad  theory,  now  broached  and  daily 
growing  in  strength  and  clearness — daily,  indeed,  gaining 
more  and  more  of  assent  from  the  most  successful  workers 
and  profound  thinkers  of  the  medical  profession  itself — 


ON   DUST  AND   DISEASE.  17J 

the  theory,  namely,  that  contagious  disease,  generally,  is  of 
this  parasitic  character.  Had  I  any  cause  to  regret  having 
introduced  this  theory  to  your  notice  more  than  a  year  ago, 
that  regret  should  now  be  expressed.  I  would  certainly 
renounce  in  your  presence  whatever  leaning  towards  the 
germ  theory  my  words  might  then  have  betrayed.  But 
since  the  time  referred  to  I  have  heard  or  read  nothing 
which  shakes  my  conviction  of  the  truth  of  the  theory. 
Let  me  briefly  state  the  grounds  on  which  its  supporters 
rely.  From  their  respective  viruses  you  may  plant  typhoid 
fever,  scarlatina,  or  small-pox.  What  is  the  crop  that 
arises  from  this  husbandry?  As  surely  as  a  thistle  rises 
from  a  thistle  seed,  as  surely  as  the  fig  comes  from  the  fig, 
the  grape  from  the  grape,  the  thorn  from  the  thorn,  so 
surely  does  the  typhoid  virus  increase  and  multiply 
into  typhoid  fever,  the  scarlatina  virus  into  scarlatina,  the 
small-pox  virus  into  small-pox.  What  is  the  conclusion 
that  suggests  itself  here?  It  is  this:  That  the  thing 
which  we  vaguely  call  a  virus  is  to  all  intents  and  purposes 
a  seed :  that,  excluding  the  notion  of  vitality,  in  the  whole 
range  of  chemical  science  you  cannot  point  to  an  action 
which  illustrates  this  perfect  parallelism  with  the  pheno- 
mena of  life — this  demonstrated  power  of  self-multiplica- 
tion and  reproduction.  The  germ  theory  alone  accounts 
for  the  phenomena. 

In  cases  of  epidemic  disease,  it  is  net  on  bad  air  or 
foul  drains  that  the  attention  of  the  physician  of  the  future 
will  primarily  be  fixed,  but  upon  disease  germs,  which  no 
bad  air  or  foul  drains  can  create,  but  Avhich  may  be  pushed 
by  foul  air  into  virulent  energy  of  reproduction.  You 
may  think  I  am  treading  on  dangerous  ground,  that  I  am 
putting  forth  views  that  may  interfere  with  salutary  prac- 
tice. No  such  thing.  If  you  wish  to  learn  the  impotence 
of  medical  practice  in  dealing  with  contagious  diseases, 
you  have  only  to  refer  to  a  recent  Harveian  oration  by 
10 


172  FEAGMENTS   OF   SCIENCE. 

Dr.  Gull.  Such  diseases  defy  the  physician.  They  must 
run  their  course,  and  the  utmost  that  can  be  done  for 
them  is  careful  nursing.  And  this,  though  I  do  not 
specially  insist  upon  it,  would  favour  the  idea  of  their 
vital  origin.  For  if  the  seeds  of  contagious  disease  be 
themselves  living  things,  it  may  be  difficult  to  destroy 
either  them  or  their  progeny,  without  involving  their  living 
habitat  in  the  same  destruction. 

It  has  been  said,  and  it  is  sure  to  be  repeated,  that  I 
am  quitting  my  own  metier,  in  speaking  of  these  things. 
Not  so.  I  am  dealing  with  a  question  on  which  minds 
accustomed  to  weigh  the  value  of  experimental  evidence 
are  alone  competent  to  decide,  and  regarding  which,  in  its 
present  condition,  minds  so  trained  are  as  capable  of  form- 
ing an  opinion  as  regarding  the  phenomena  of  magnetism 
or  radiant  heat.  'The  germ  theory  of  disease,'  it  has  been 
said,  'appertains  to  the  biologist  and  the  physician.' 
Granted.  But  where  is  the  biologist  or  physician,  whose 
researches,  in  connection  with  this  subject,  could  for  one 
instant  be  compared  to  those  of  the  chemist  Pasteur  ?  It 
is  not  the  philosophic  members  of  the  medical  profession 
who  are  dull  to  the  reception  of  truth  not  originated  with- 
in the  pale  of  the  profession  itself.  I  cannot  better  con- 
clude this  portion  of  my  story  than  by  reading  to  you  an 
extract  from  a  letter  addressed  to  me  some  time  ago  by 
Dr.  William  Budd,  of  Clifton,  to  whose  insight  and  energy 
the  town  of  Bristol  owes  so  much  in  the  way  of  sanitary 
improvement. 

'  As  to  the  germ  theory  itself,'  writes  Dr.  Budd,  *  that 
is  a  matter  on  which  I  have  long  since  made  up  my  mind. 
From  the  day  when  I  first  began  to  think  of  these  subjects, 
I  had  never  had  a  doubt  that  the  specific  cause  of  conta- 
gious fevers  must  be  living  organisms. 

'  It  is  impossible,  in  fact,  to  make  any  statement  bear- 
ing upon  the  essence  or  distinctive  characters  of  these 


ON   DUST   AND   DISEASE.  173 

fevers,  without  using  terms  which  are  of  all  others  the 
most  distinctive  of  life.  Take  up  the  writings  of  the 
most  violent  opponent  of  the  germ  theory,  and,  ten  to  one, 
you  will  find  them  full  of  such  terms  as  "  propagation," 
"self-propagation,"  "  reproduction,"  " self-multiplication," 
and  so  on.  Try  as  he  may — if  he  has  anything  to  say  of 
those  diseases  which  is  characteristic  of  them — he  cannot 
evade  the  use  of  these  terms,  or  the  exact  equivalents  to 
them.  While  perfectly  applicable  to  living  things,  these 
terms  express  qualities  which  are  not  only  inapplicable  to 
common  chemical  agents,  but,  as  far  as  I  can  see,  actually 
inconceivable  of  them.' 

Cotton-wool  Respirator. 

Once,  then,  established  within  the  body,  this  evil  form 
of  life,  if  you  will  allow  me  to  call  it  so,  must  run  its 
course.  Medicine  as  yet  is  powerless  to  arrest  its  progress, 
and  the  great  point  to  be  aimed  at  is  to  prevent  its  access 
to  the  body.  It  was  with  this  thought  in  my  mind  that 
I  ventured  to  recommend,  more  than  a  year  ago,  the  use 
of  cotton-wool  respirators  in  infectious  places.  I  would 
here  repeat  my  belief  in  their  efficacy  if  properly  con- 
structed. But  I  do  not  wish  to  prejudice  the  use  of  these 
respirators,  by  connecting  them  indissolubly  with  the  germ 
theory.  There  are  too  many  trades  in  England  where  life 
is  shortened  and  rendered  miserable  by  the  introduction 
of  matters  into  the  lungs  which  might  be  kept  out  of  them. 
Dr.  Grreenhow  has  shown  the  stony  grit  deposited  in  the 
lungs  of  stonecutters.  The  black  lungs  of  colliers  is  an- 
other case  in  point.  In  fact,  a  hundred  obvious  cases 
might  be  cited,  and  others  that  are  not  obvious  might  be 
added  to  them.  We  should  not,  for  example,  think  that 
printing  implied  labours  where  the  use  of  cotton-wool 
"espirators  might  come  into  play ;  but  the  fact  is  that  the 


174  FRAGMENTS   OP  SCIENCE. 

dust  arising  from  the  sorting  of  the  type  is  very  destructive 
of  health.  I  went  some  time  ago  into  a  manufactory  in 
one  of  our  large  towns,  where  iron  vessels  are  enamelled  by 
coating  them  with  a  mineral  powder,  and  subjecting  them 
to  a  heat  sufficient  to  fuse  the  powder.  The  organisation 
of  the  establishment  was  excellent,  and  one  thing  only  was 
needed  to  make  it  faultless.  In  a  large  room  a  number 
of  women  were  engaged  covering  the  vessels.  The  air 
was  laden  with  the  fine  dust,  and  their  faces  appeared  as 
white  and  bloodless  as  the  powder  with  which  they  worked. 
By  the  use  of  cotton-wool  respirators  these  women  might 
be  caused  to  breathe  air  as  free  from  suspended  matter  as 
that  of  the  open  street.  Over  a  year  ago  a  Lancashire 
seedsman  wrote  to  me,  stating  that  during  the  seed 
season  his  men  suffered  horribly  from  irritation  and  fever, 
so  that  many  of  them  left  his  service.  He  asked  for  help, 
and  I  gave  him  my  advice.  At  the  conclusion  of  the  sea- 
son, this  year,  he  wrote  to  inform  me  that  he  had  folded 
a  little  cotton-wool  in  muslin,  and  tied  it  in  front  of  the 
mouth  ;  and  that  with  this  simple  defence  he  had  passed 
through  the  season  in  comfort,  and  without  a  single  com- 
plaint from  his  men. 

Against  the  use  of  such  a  respirator  the  obvious  objec- 
tion arises,  that  it  becomes  wet  and  heated  by  the  breath. 
While  I  was  casting  about  for  a  remedy  for  this  a  friend  for- 
warded to  me  from  Newcastle  a  form  of  respirator  invented 
by  Mr.  Carrick,  a  hotel-keeper  at  Glasgow,  which,  by  a 
slight  modification,  may  be  caused  to  meet  the  case 
perfectly.  The  respirator,  with  its  back  in  part  removed, 
is  shown  in  fig.  4.  Under  the  partition  of  wire-gauze 
q  r,  is  a  space  intended  by  Mr.  Carrick  for  « medicated 
substances,'  and  which  may  be  filled  with  cotton-wool 
The  mouth  is  placed  against  the  aperture  0,  which  fits 
closely  round  the  lips,  and  the  filtered  air  enters  the 
mouth  through  a  light  valve  V,  which  is  lifted  by  the  act 


ON   DUST   AND   DISEASE.  175 

of  inhalation.     During  exhalation  this  valve  closes ;  the 
breath  escapes  by  a  second  valve,  v,  into  the  open  air. 

Fio.  4. 


The  wool  is  thus  kept  dry  and  cool ;  the  air  in  passing  through 
it  being  filtered  of  everything  it  holds  in  suspension. 

Fireman's  Respirator. 

We  have  thus  been  led  by  our  first  unpractical  experi- 
ments into  a  thicket  of  practical  considerations.  But 
another  step  is  possible.  Admiring,  as  I  do,  the  bravery 
of  our  firemen,  and  hearing  that  smoke  was  a  more 
serious  enemy  than  flame  itself,  I  thought  of  devising  a 
fireman's  respirator. 

Our  fire-escapes  are  each  in  charge  of  a  single  man, 
and  it  would  be  of  obvious  importance  to  place  it 
in  the  power  of  each  of  those  men  to  penetrate  through 
the  densest  smoke,  into  the  recesses  of  a  house,  and 
there  to  rescue  those  who  would  otherwise  be  suffocated 
or  burnt.  Cotton-wool,  which  so  effectually  arrested 
dust,  was  first  tried;  but,  though  found  soothing  in 
certain  gentle  kinds  of  smoke,  it  was  no  match  for  the 
pungent  fumes  of  a  resinous  fire,  which  evolves  a  most 
abominable  smoke.  For  the  purpose  of  catching  the 


176  FRAGMENTS    OF   SCIENCE. 

atmospheric  germs,  M.  Pouchet  spread  a  film  of  glycerine 
on  a  plate  of  glass,  urged  air  against  the  film,  and  ex- 
amined the  dust  which  stuck  to  it.  The  moistening  of 
the  cotton-wool  with  this  substance  was  a  decided  improve- 
ment ;  still  the  respirator  only  enabled  us  to  remain  in 
dense  smoke  for  three  or  four  minutes,  after  which  the 
irritation  became  unendurable.  Eeflection  suggested 
that,  in  combustion  so  imperfect  as  the  production  of 
dense  smoke  implies,  there  must  be  numerous  hydro- 
carbons produced,  which,  being  in  a  state  of  vapour,  would 
be  very  imperfectly  arrested  by  the  cotton-wool.  These, 
in  all  probability,  were  the  cause  of  the  residual  irritation ; 
and  if  these  could  be  removed,  a  practically  perfect  res- 
pirator might  possibly  be  obtained. 

I  state  the  reasoning  exactly  as  it  occurred  to  my  mind. 
Its  result  will  be  anticipated  by  many  present.  All 
bodies  possess  the  power  of  condensing,  in  a  greater  or 
less  degree,  gases  and  vapours  upon  their  surfaces,  and 
when  the  condensing  body  is  very  porous,  or  in  a  fine  state 
of  division,  the  force  of  condensation  may  produce  very 
remarkable  effects.  Thus,  a  clean  piece  of  platinum-foil 
placed  in  a  mixture  of  oxygen  and  hydrogen  so  squeezes 
the  gases  together  as  to  cause  them  to  combine ;  and  if 
the  experiment  be  made  with  care,  the  heat  of  combination 
may  raise  the  platinum  to  bright  redness.  The  prompt- 
ness of  this  action  is  greatly  augmented  by  reducing  the 
platinum  to  a  state  of  fine  division.  A  pellet  of  « spongy 
platinum,'  for  instance,  plunged  into  a  mixture  of  oxygen 
and  hydrogen,  causes  the  gases  to  explode  instantly.  In 
virtue  of  its  extreme  porosity,  a  similar  power  is  possessed 
by  charcoal.  It  is  not  strong  enough  to  cause  the  oxygen 
and  hydrogen  to  combine  like  the  spongy  platinum,  but 
it  so  squeezes  the  more  condensable  vapours,  and  q,cts  with 
such  condensing  power  upon  the  oxygen  of  the  air,  as  to 
bring  both  within  the  combining  distance,  thus  enabling 


ON   DUST   AND   DISEASE.  177 

the  oxygen  to  attack  and  destroy  the  vapours  in  the  pores 
of  the  charcoal.  In  this  way,  effluvia  of  all  kinds  may  be 
virtually  burnt  up  ;  and  this  is  the  principle  of  the  excel- 
lent charcoal  respirators  invented  by  Dr.  Stenhouse. 
Armed  with  one  of  these,  you  may  go  into  the  foulest- 
smelling  places  without  having  your  nose  offended. 

But,  while  powerful  to  arrest  vapours,  the  charcoal  res- 
pirator is  ineffectual  as  regards  smoke.  The  smoke-parti- 
cles get  freely  through  the  respirator.  With  a  number  of 
such  respirators,  tested  downstairs,  from  half  a  minute  to 
a  minute  was  the  limit  of  endurance.  This  might  be 
exceeded  by  Faraday's  simple  method  of  emptying  the 
lungs  completely,  and  then  filling  them  before  going  into 
a  smoky  atmosphere.  In  fact,  each  solid  smoke  particle 
is  itself  a  bit  of  charcoal,  and  carries  on  it,  and  in  it,  its 
little  load  of  irritating  vapour.  It  is  this,  far  more  than 
the  particles  of  carbon  themselves,  that  produces  the  irri- 
tation. Hence  two  causes  of  offence  are  to  be  removed : 
the  carbon  particles  which  convey  the  irritant  by  adhesion 
and  condensation,  and  the  free  vapour  which  accompanies 
the  particles.  The  moistened  cotton-wool  I  knew  would 
arrest  the  first ;  fragments  of  charcoal  I  hoped  would  stop 
the  second.  In  the  first  fireman's  respirator,  Mr.  Carrick's 
arrangement  of  two  valves,  the  one  for  inhalation,  the 
other  for  exhalation,  are  preserved.  But  the  portion  of  it 
which  holds  the  filtering  and  absorbent  substances,  is 
prolonged  to  a  depth  of  four  or  five  inches  (see  fig.  5). 
Under  the  partition  of  wire-gauze  q  r  at  the  bottom  of 
the  space  which  fronts  the  mouth  is  placed  a  layer  of 
cotton-wool,  c,  moistened  with  glycerine ;  then  a  thin 
layer  of  dry  wool,  cf  ;  then  a  layer  of  charcoal  fragments ; 
and  finally  a  second  thin  layer  of  dry  cotton-wool.  The 
succession  of  the  layers  may  be  changed  without  prejudice 
to  the  action.  A  wire-gauze  cover,  shown  in  plan  below 
3g.  5,  keeps  the  substances  from  falling  out  of  the  respi- 


178 


FRAGMENTS   OF   SCIENCE. 


rator.     A  layer  of  caustic  lime  has  been  added  for  the 
absorption  of  carbonic  acid;  but  in  the  densest  smoke 


FIG.  5. 


fete. 


that  we  have  hitherto  employed,  it  has  not  been  found  ne- 
cessary, nor  is  it  shown  in  the  figure.     In  a  flaming  build- 


ON  DUST   AND    DISEASE.  179 

ing,  indeed,  the  mixture  of  air  with  the  smoke  never 
permits  the  carbonic  acid  to  become  so  dense  as  to  be 
irrespirable;  but  in  a  place  where  the  gas  is  present  in 
undue  quantity,  the  fragments  of  lime  would  materially 
mitigate  its  action. 

In  a  small  cellar-like  chamber  with  a  stone  flooring 
and  stone  walls,  the  first  experiments  were  made.  We 
placed  there  furnaces  containing  resinous  pine-wood, 
lighted  the  wood,  and,  placing  over  it  a  lid  which  pre- 
vented too  brisk  a  circulation  of  the  air,  generated  dense 
volumes  of  smoke.  With  our  eyes  protected  by  suitable 
glasses,  my  assistant  and  I  have  remained  for  half  an 
hour  and  more  in  smoke  so  dense  and  pungent  that  a 
single  inhalation,  through  the  undefended  mouth,  would 
be  perfectly  unendurable.  We  might  have  prolonged  our 
stay  for  hours.  Having  thus  far  perfected  the  instru- 
ment, I  wrote  to  the  chief  officer  of  the  Metropolitan  Fire 
Brigade,  asking  him  whether  such  a  respirator  would  be 
of  use  to  him.  His  reply  was  prompt ;  it  would  be  most 
valuable.  He  had,  however,  made  himself  acquainted 
with  every  contrivance  of  the  kind  in  this  and  other 
countries,  and  had  found  none  of  them  of  any  practical 
use.  He  offered  to  come  and  test  it  here,  or  to  place  a 
room  at  my  disposal  in  the  City.  At  my  request  he 
came  here,  accompanied  by  three  of  his  men.  Our  small 
room  was  filled  with  smoke  to  their  entire  satisfaction. 
The  three  men  went  successively  into  it,  and  remained 
there  as  long  as  Captain  Shaw  wished  them.  On  coming 
out  they  said  that  they  had  not  suffered  the  slightest  in- 
convenience ;  that  they  could  have  remained  all  day  in 
the  smoke.  Captain  Shaw  then  tested  the  respirator 
with  the  same  result,  and  he  afterwards  took  great  interest 
in  the  perfecting  of  the  instrument. 

Various  ameliorations  and  improvements  have  recently 


180  FRAGMENTS   OF   SCIENCE. 

been  introduced  into  the  smoke  respirator.  The  hood  of 
Captain  Shaw  has  been  improved  upon  by  the  simple  and 
less  expensive  mouthpiece  of  Mr.  Sinclair  ;  and  this,  in  its 
turn,  has  been  simplified  and  improved  by  my  assistant 
Mr.  John  Cottrell.  The  respirator  is  now  in  considerable 
demand,  and  it  has  already  done  good  practical  service. 
Care  is,  however,  necessary  in  moistening  the  wool  with 
glycerine.  It  must  be  carefully  teazed,  so  that  the  indi- 
vidual fibres  may  be  moistened,  and  clots  must  be  avoided. 
I  cannot  recommend  the  layers  of  moistened  flannel 
which,  in  some  cases,  have  been  used  instead  of  cotton- 
wool :  nothing  equals  the  wool,  when  carefully  treated. 

An  experiment  made  last  year  brought  out  very  con- 
spicuously the  necessity  of  careful  packing,  and  the  enor- 
mous comparative  power  of  resisting  smoke  irritation 
possessed  by  our  firemen,  and  the  able  officer  who  com- 
mands them.  Having  heard  from  Captain  Shaw  that,  in 
some  recent  very  trying  experiments,  he  had  obtained  the 
best  effects  from  dry  cotton-wool,  and  thinking  that  I 
could  not  have  been  mistaken  in  my  first  results,  which 
proved  the  dry  so  much  inferior  to  the  moistened  wool 
and  its  associated  charcoal,  I  proposed  to  Captain  Shaw  to 
bring  the  matter  to  a  test  at  his  workshops  in  the  City. 
He  was  good  enough  to  accept  my  proposal,  and  thither  I 
went  on  May  7,  1874.  The  smoke  was  generated  in  a 
confined  space  from  wet  straw,  and  it  was  certainly  very  dia- 
bolical. At  this  season  of  the  year  I  am  usually  somewhat 
shorn  of  vigour,  and  therefore  not  in  the  best  condition 
for  severe  experiments ;  still  I  wished  to  test  the  matter 
in  my  own  person.  With  a  respirator  which  had  been  in 
use  some  days  previously,  and  which  was  not  carefully 
packed,  I  followed  a  fireman  into  the  smoke,  he  being 
provided  with  a  dry-wool  respirator.  I  was  compelled  to 
quit  the  place  in  about  three  minutes,  while  the  fireman 
remained  there  for  six  or  seven  minutes. 


ON   DUST  AND   DISEASE.  181 

I  then  tried  his  respirator  upon  myself,  and  found 
that  with  it  I  could  not  remain  more  than  a  minute  in 
the  smoke  ;  in  fact  the  first  inhalation  provoked  coughing. 

Thinking  that  Captain  Shaw  himself  might  have  lungp 
more  like  mine  than  those  of  his  fireman,  I  proposed  that 
we  should  try  the  respirators  together ;  but  he  informed 
me  that  his  lungs  were  very  strong.  He  was,  however, 
good  enough  to  accede  to  my  request.  Before  entering 
the  den  a  second  time  I  repacked  my  respirator,  with 
due  care,  and  entered  the  smoke  in  company  with  Captain 
Shaw.  I  could  hear  him  breathe  long  slow  inhalations  ;  his 
labour  was  certainly  greater  than  mine,  and  after  the 
!apse  of  seven  minutes  I  heard  him  cough.  In  seven  and 
a  half  minutes  he  had  to  quit  the  place,  thus  proving  that 
his  lungs  were  able  to  endure  the  irritation  seven  times  as 
long  as  mine  could  bear  it.  I  continued  in  the  smoke, 
with  hardly  any  discomfort,  for  sixteen  minutes,  and  cer- 
tainly could  have  remained  in  it  much  longer.  The 
advantage  arising  from  the  glycerine  was  thus  placed 
beyond  question. 

During  this  time  I  was  in  a  condition  to  render  very 
material  assistance  to  a  person  in  danger  of  suffocation. 

Helmholtz  on  llay  Fever. 

In  my  lecture  on  Dust  and  Disease  in  1870,  I  referred 
to  an  experiment  made  by  Helmholtz  upon  himself  which 
strikingly  connected  hay  fever  with  animalcular  life. 
About  a  year  ago  I  received  from  Professor  Binz  of  Bonn 
a  short,  but  important  paper,  embracing  Helmholtz's 
account  of  his  observation,  to  which  Professor  Binz  has 
added  some  remarks  of  his  own.  The  paper,  being 
mainly  intended  for  English  medical  men,  was  published 
in  English,  and  though  here  and  there  its  style  might  be 
amended,  I  think  it  better  to  publish  it  unaltered  here. 


182  FRAGMENTS   OF   SCIENCE. 

From  what  I  have  observed  (says  Professor  Binz)  of  re- 
cent English  publications  on  the  subject  of  hay  fever,  I  am 
led  to  suppose  that  English  authorities  are  inaccurately  ac- 
quainted with  the  discovery  of  Professor  Helmholtz,  as  far 
back  as  1868,  of  the  existence  of  uncommon  low  organisms 
in  the  nasal  secretions  in  this  complaint,  and  of  the 
possibility  of  arresting  their  action  by  the  local  employ- 
ment of  quinine.  I  therefore  purpose  to  republish  the 
letter  in  which  he  originally  announced  these  facts  to  my- 
self, and  to  add  some  further  observations  on  this  topic. 
The  letter  is  as  follows : ! — 

4 1  have  suffered,  as  well  as  I  can  remember,  since  the 
year  1847,  from  the  peculiar  catarrh  called  by  the  English 
"  hay  fever,"  the  speciality  of  which  consists  in  its  attack- 
ing its  victims  regularly  in  the  hay  season  (myself  between 
May  20  and  the  end  of  June),  that  it  ceases  in  the  cooler 
weather,  but  on  the  other  hand  quickly  reaches  a  great 
intensity  if  the  patients  expose  themselves  to  heat  and 
sunshine.  An  extraordinarily  violent  sneezing  then  sets 
in,  and  a  strongly  corrosive  thin  discharge,  with  which 
much  epithelium  is  thrown  off.  This  increases,  after  a 
few  hours,  to  a  painful  inflammation  of  the  mucous  mem- 
brane and  of  the  outside  of  the  nose,  and  excites  fever 
with  severe  headache  and  great  depression,  if  the  patient 
cannot  withdraw  himself  from  the  heat  and  the  sunshine. 
In  a  cool  room,  however,  these  symptoms  vanish  as  quickly 
as  they  come  on,  and  there  then  only  remains  for  a  few 
days  a  lessened  discharge  and  soreness,  as  if  caused  by 
the  loss  of  epithelium.  I  remark,  by  the  way,  that  in  all 
my  other  years  I  had  very  little  tendency  to  catarrh  or 
catching  cold,  while  the  hay  fever  has  never  failed  during 
the  twenty-one  years  of  which  I  have  spoken,  and  has 
never  attacked  me  earlier  or  later  in  the  year  than  the 

'  Of.  VirchoVs  '  Archiv.'  vol.  xlvi.  p.  100. 


ON   DUST   AND   DISEASE.  183 

times  named.  The  condition  is  extremely  troublesome, 
and  increases,  if  one  is  obliged  to  be  much  exposed  to  the 
sun,  to  an  excessively  severe  malady. 

1  The  curious  dependence  of  the  disease  on  the  season 
of  the  year  suggested  to  me  the  thought  that  organisms 
might  be  the  origin  of  the  mischief.  In  examining  the 
secretion  I  regularly  found,  in  the  last  five  years,  certain 
vibrio-like  bodies  in  it,  which  at  other  times  I  could  not 
observe  in  my  nasal  secretion.  .  .  .  They  are  very  small, 
and  can  only  be  recognised  with  the  immersion-lens  of  a 
very  good  Hartnack's  microscope.  It  is  characteristic  of 
the  common  isolated  single  joints  that  they  contain  four 
nuclei  in  a  row,  of  which  two  pairs  are  more  closely 
united.  The  length  of  the  joints  is  0'004  millimetre. 
Upon  the  warm  objective-stage  they  move  with  moderate 
activity,  partly  in  mere  vibration,  partly  shooting  back- 
wards and  forwards  in  the  direction  of  their  long  axis  ;  in 
lower  temperatures  they  are  very  inactive.  Occasionally 
one  finds  them  arranged  in  rows  upon  each  other,  or  in 
branching  series.  Observed  some  days  in  the  moist 
chamber,  they  vegetated  again,  and  appeared  somewhat 
larger  and  more  conspicuous  than  immediately  after  their 
excretion.  It  is  to  be  noticed  that  only  that  kind  of 
secretion  contains  them  which  is  expelled  by  violent 
sneezings ;  that  which  drops  slowly  does  not  contain 
any.  They  stick  tenaciously  enough  in  the  lower  cavities 
and  recesses  of  the  nose. 

'  When  I  saw  your  first  notice  respecting  the  poisonous 
action  of  quinine  upon  infusoria,  I  determined  at  once  to 
make  an  experiment  with  that  substance,  thinking  that 
these  vibrionic  bodies,  even  if  they  did  not  cause  the 
whole  illness,  still  could  render  it  much  more  unpleasant 
through  their  movements  and  the  decompositions  caused 
by  them.  For  that  reason  I  made  a  neutral  solution  of 
sulphate  of  quinine,  which  did  not  contain  much  of  the 


184  FRAGMENTS   OF  SCIENCE. 

salt  (1'800),  but  still  was  effective  enough,  and  caused 
moderate  irritation  on  the  mucous  membrane  of  the  nose. 
I  then  lay  flat  on  my  back,  keeping  my  head  very  low,  and 
poured  with  a  pipette  abou£  four  cubic  centimetres  into 
both  nostrils.  Then  I  turned  my  head  about  in  order  to 
let  the  liquid  flow  in  all  directions. 

1  The  desired  effect  was  obtained  immediately,  and  re- 
mained for  some  hours ;  I  could  expose  myself  to  the  sun 
without  fits  of  sneezing  and  the  other  disagreeable  symp- 
toms coming  on.  It  was  sufficient  to  repeat  the  treatment 
three  times  a  day,  even  under  the  most  unfavourable  cir- 
cumstances, in  order  to  keep  myself  quite  free.1  There 
were  then  no  such  vibrios  in  the  secretion.  If  I  only  go 
out  in  the  evening,  it  suffices  to  inject  the  quinine  once  a 
day,  just  before  going.  After  continuing  this  treatment 
for  some  days  the  symptoms  disappear  completely,  but  if 
I  leave  off  they  return  till  towards  the  end  of  June. 

'My  first  experiments  with  quinine  date  from  the 
summer  of  1867  ;  this  year  (1868)  I  began  at  once  as  soon 
as  the  first  traces  of  the  illness  appeared,  and  I  have  thus 
been  able  to  stop  its  development  completely. 

'  I  have  hesitated  as  yet  in  publishing  the  matter,  be- 
cause I  have  found  no  other  patient2  on  whom  I  could  try 
the  experiment.  There  is,  it  seems  to  me,  no  doubt,  con- 
sidering the  extraordinary  regularity  in  the  recurrence  and 
course  of  the  illness,  that  quinine  had  here  a  most  quick 
and  decided  effect.  And  this  again  makes  my  hypothesis 
very  probable,  that  the  vibrios,  even  if  being  no  specific 
form  but  a  very  frequent  one,  are  at  least  the  cause  of  the 
rapid  increase  of  the  symptoms  in  warm  air,  as  heat  excites 
them  to  lively  action.' 

1  There  is  no  foundation  for  the  objection  that  syringing  the  nose 
could  not  cure  the  asthma  which  accompanies  hay  fover ;  for  this  asthma 
is  only  the  reflex  effect  arising  from  the  irritation  of  the  nose. — 13. 

3  Helmholtz,  now  Professor  of  Physics  at  the  University  of  Berlin,  is, 
although  M.D.,  no  medical  practitioner.' — B. 


ON  DUST  AND   DISEASE.  185 

I  should  be  very  glad  if  the  above  lines  would  induce 
medical  men  in  England — the  haunt  of  hay  fever — to  test 
the  observation  of  Helmholtz.  To  most  patients  the  ap- 
plication with  the  pipette  may  be  too  difficult  or  impos- 
sible ;  I  have  therefore  already  suggested  the  use  of 
Weber's  very  simple  but  effective  nose-douche.  Also  it 
will  be  advisable  to  apply  the  solution  of  quinine  tepid. 
It  can,  further,  not  be  repeated  often  enough  that  quinine 
is  frequently  adulterated,  especially  with  cinchonia,  the 
action  of  which  is  much  less  to  be  depended  upon. 

Dr.  Frickhofer,  of  Schwalbach,  has  communicated  to 
me  a  second  case  in  which  hay  fever  was  cured  by  local 
application  of  quinine.1  Professor  Busch,  of  Bonn,  autho- 
rises me  to  say  that  he  succeeded  in  two  cases  of  '  catarrhus 
aestivus '  by  the  same  method :  a  third  patient  was  obliged 
to  abstain  from  the  use  of  quinine,  as  it  produced  an  un- 
bearable irritation  of  the  sensible  nerves  of  the  nose.  In 
the  autumn  of  1872  Helmholtz  told  me  that  his  fever  was 
quite  cured,  and  that  in  the  meantime  two  other  patients 
had,  by  his  advice,  tried  this  method,  and  with  the  same 
success. 

1  Cf.  Virchow's  'Archiv.'  (1870),  vol.  li.  p.  176. 


188  FRAGMENTS   OF   SCIENCE. 


VI. 

VOYAGE  TO  ALGERIA   TO   OBSERVE   THE  ECLIPSE. 
1870. 

THE  opening  of  the  Eclipse  Expedition  was  not  pro- 
pitious. Portsmouth,  on  December  5,  1870,  was 
swathed  by  a  fog,  which  was  intensified  by  smoke,  and 
traversed  by.  a  drizzle  of  fine  rain.  At  six  P.M.  I  was  on 
board  the  '  Urgent.'  On  Tuesday  morning  the  weather 
was  too  thick  to  permit  of  the  ship's  being  swung  and 
her  compasses  calibrated.  The  Admiral  of  the  port,  a 
man  of  very  noble  presence,  came  on  board.  Under 
his  stimulus  the  energy  which  the  weather  had  damped 
appeared  to  become  more  active,  and  soon  after  his  de- 
parture we  steamed  down  to  Spithead.  Here  the  fog 
had  so  far  lightened  as  to  enable  the  officers  to  swing  the 
ship. 

At  three  P.M.  on  Tuesday,  December  6,  we  got  away, 
gliding  successively  past  Whitecliff  Bay,  Bembridge, 
Sandown,  Shanklin,  Ventnor,  and  St.  Catherine's  Light- 
house. On  "Wednesday  morning  we  sighted  the  Isle  of 
Ushant,  on  the  French  side  of  the  Channel.  The  northern 
end  of  the  island  has  been  fretted  by  the  waves  into  de- 
tached tower-like  masses  of  rock  of  very  remarkable  ap- 
pearance. In  the  Channel  the  sea  was  green,  and  opposite 
Ushant  it  was  a  brighter  green.  On  Wednesday  evening 
we  committed  ourselves  to  the  Bay  of  Biscay.  The  roll 
of  the  Atlantic  was  full,  but  not  violent.  There  had  been 
scarcely  a  gleam  of  sunshine  throughout  the  day,  but  the 


VOYAGE   TO   ALGERIA.  187 

cloud-forms  were  fine,  and  their  apparent  solidity  impres- 
sive. On  Thursday  morning  the  green  of  the  sea  was 
displaced  by  a  deep  indigo  blue.  The  whole  of  Thursday 
we  steamed  across  the  bay.  We  had  little  blue  sky,  but 
the  clouds  were  again  grand  and  varied — cirrus,  stratus, 
cumulus,  and  nimbus,  we  had  them  all.  Dusky  hair-like 
trails  were  sometimes  dropped  from  the  distant  clouds 
to  the  sea.  These  were  falling  showers,  and  they  some- 
times occupied  the  whole  horizon,  while  we  steamed 
across  the  rainless  circle  which  was  thus  surrounded. 
Sometimes  we  plunged  into  the  rain,  and  once  or 
twice,  by  slightly  changing  our  course,  avoided  a  heavy 
shower.  From  time  to  time  perfect  rainbows  spanned 
the  heavens  from  side  to  side.  At  times  a  bow  would 
appear  in  fragments,  showing  the  keystone  of  the  arch 
midway  in  air,  and  its  two  buttresses  on  the  horizon. 
In  all  cases  the  light  of  the  bow  could  be  quenched  by 
a  Nicol's  prism,  with  its  long  diagonal  tangent  to  the 
arc.  Sometimes  gleaming  patches  of  the  firmament  were 
seen  amid  the  clouds.  When  viewed  in  the  proper  direc- 
tion, the  gleam  could  be  quenched  by  a  Nicol's  prism,  a 
dark  aperture  being  thus  opened  into  stellar  space. 

At  sunset  on  Thursday  the  denser  clouds  were  fiercely 
fringed,  while  through  the  lighter  ones  seemed  to  issue 
the  glow  of  a  conflagration.  On  Friday  morning  we 
sighted  Cape  Finisterre — the  extreme  end  of  the  arc  which 
sweeps  from  Ushant  round  the  Bay  of  Biscay.  Calm  spaces 
of  blue,  in  which  floated  quietly  scraps  of  cumuli,  were 
behind  us,  but  in  front  of  us  was  a  horizon  of  portentous 
darkness.  It  continued  thus  threatening  throughout  the 
day.  Towards  evening  the  wind  strengthened  to  a  gale, 
and  at  dinner  it  was  difficult  to  preserve  the  plates  and 
dishes  from  destruction.  Our  thinned  company  hinted 
that  the  rolling  had  other  consequences.  It  was  very  wild 
when  we  went  to  bed.  I  slumbered  and  slept  but  after 


188  FRAGMENTS   OF   SCIENCE. 

some  time  was  rendered  anxiously  conscious  that  my  body 
had  become  a  kind  of  projectile,  with  the  ship's  side 
for  a  target.  I  gripped  the  edge  of  my  berth  to  save 
myself  from  being  thrown  out.  Outside,  I  could  hear 
somebody  say  that  he  had  been  thrown  from  his  berth, 
and  sent  spinning  to  the  other  side  of  the  saloon.  The 
screw  laboured  violently  amid  the  lurching  ;  it  incessantly 
quitted  the  water,  and,  twirling  in  the  air,  rattled  against 
its  bearings,  and  caused  the  ship  to  shudder  from  stem  to 
stern.  At  times  the  waves  struck  us,  not  with  the  soft 
impact  which  might  be  expected  from  a  liquid,  but  with 
the  sudden  solid  shock  of  battering-rams.  *  No  man 
knows  the  force  of  water,'  said  one  of  the  officers,  '  until 
he  has  experienced  a  storm  at  sea.'  These  blows  followed 
each  other  at  quicker  intervals,  the  screw  rattling  after 
each  of  them,  until,  finally,  the  delivery  of  a  heavier 
stroke  than  ordinary  seemed  to  reduce  the  saloon  to  chaos. 
Furniture  crashed,  glasses  rang,  and  alarmed  enquiries 
immediately  followed.  Amid  the  noises  I  heard  one  note 
of  forced  laughter;  it  sounded  very  ghastly.  Men 
tramped  through  the  saloon,  and  busy  voices  were  heard 
aft,  as  if  something  there  had  gone  wrong. 

I  rose,  and  not  without  difficulty  got  into  my  clothes. 
In  the  after-cabin,  under  the  superintendence  of  the  able 
and  energetic  navigating  lieutenant,  Mr.  Brown,  a  group 
of  blue-jackets  were  working  at  the  tiller-ropes.  These 
had  become  loose,  and  the  helm  refused  to  answer  the 
wheel.  High  moral  lessons  might  be  gained  on  shipboard, 
by  observing  what  steadfast  adherence  to  an  object  can 
accomplish,  and  what  large  effects  are  heaped  up  by  the 
addition  of  infinitesimals.  The  tiller-rope,  as  the  blue- 
jackets strained  in  concert,  seemed  hardly  to  move  ;  still 
it  did  move  a  little,  until  finally,  by  timing  the  pull  to 
the  lurching  of  the  ship,  the  mastery  of  the  rudder  was 
obtained.  I  had  previously  gone  on  deck.  Eound  the 


VOYAGE   TO   ALGERIA.  189 

saloon-door  were  a  few  members  of  the  eclipse  party,  who 
seemed  in  no  mood  for  scientific  observation.  Nor  did  I ; 
but  I  wished  to  see  the  storm.  I  climbed  the  steps  to  the 
poop,  exchanged  a  word  with  Captain  Toynbee,  the  only 
member  of  the  party  to  be  seen  on  the  poop,  and  by  his 
direction  made  towards  a  cleat  not  far  from  the  wheel.1 
Bound  it  I  coiled  my  arms.  With  the  exception  of  the 
men  at  the  wheel,  who  stood  as  silent  as  corpse?,  I  was 
alone. 

I  had  seen  grandeur  elsewhere,  but  this  was  a  new 
form  of  grandeur  to  me.  The  'Urgent'  is  long  and 
narrow,  and  during  our  expedition  she  lacked  the  steady- 
ing influence  of  sufficient  ballast.  She  was  for  a  time 
practically  rudderless,  and  lay  in  the  trough  of  the  sea.  I 
could  see  the  long  ridges,  with  some  hundreds  of  feet 
between  their  crests,  rolling  upon  the  ship  perfectly 
parallel  to  her  sides.  As  they  approached,  they  so  grew 
upon  the  eye  as  to  render  the  expression  <  mountains  high ' 
intelligible.  At  all  events,  there  was  no  mistaking  their 
mechanical  might,  as  they  took  the  ship  upon  their 
shoulders,  and  swung  her  like  a  pendulum.  The  deck 
sloped  sometimes  at  an  angle  which  I  estimated  at  over 
forty-five  degrees  ;  wanting  my  previous  Alpine  practice, 
I  should  have  felt  less  confidence  in  my  grip  of  the  cleat. 
Here  and  there  the  long  rollers  were  tossed  by  interference 
into  heaps  of  greater  height.  The  wind  caught  their 
crests,  and  scattered  them  over  the  sea,  the  whole  surface 
of  which  was  seething  white.  The  aspect  of  the  clouds 
was  a  fit  accompaniment  to  the  fury  of  the  ocean.  The 
inoon  was  almost  full — at  times  concealed,  at  times  re- 
vealed, as  the  scud  flew  wildly  over  it.  These  things  ap- 
pealed to  the  eye,  while  the  ear  was  filled  by  the  groaning 
of  the  screw  and  the  whistle  and  boom  of  the  storm. 

1  The  cleat  is  a  T-shaped  mass  of  metal  employed  for  the  fastening  oi 
ropes. 


190  FRAGMENTS   OP   SCIENCE. 

Nor  was  the  outward  agitation  the  cnly  object  of 
interest  to  me.  I  was  at  once  subject  and  object  to  myself, 
and  watched  with  intense  interest  the  workings  of  my  own 
mind.  The  '  Urgent '  is  an  elderly  ship.  She  had  been 
built,  I  was  told,  by  a  contracting  firm  for  some  foreign 
Government,  and  had  been  diverted  from  her  first  purpose 
when  converted  into  a  troop-ship.  She  had  been  for  some 
time  out  of  work,  and  I  had  heard  that  one  of  her  boilers, 
at  least,  needed  repair.  Our  scanty  but  excellent  crew, 
moreover,  did  not  belong  to  the  '  Urgent,'  but  had  been 
gathered  from  other  ships.  Our  three  lieutenants  were 
also  volunteers.  All  this  passed  swiftly  through  my  mind 
as  the  steamer  shook  under  the  blows  of  the  waves,  and  I 
thought  that  probably  no  one  on  board  could  say  how 
much  of  this  thumping  and  straining  the  i  Urgent '  would 
be  able  to  bear.  This  uncertainty  caused  me  to  look 
steadily  at  the  worst,  and  I  tried  to  strengthen  myself 
in  the  face  of  it. 

But  at  length  the  helm  laid  hold  of  the  water,  and  the 
ship  was  got  gradually  round  to  face  the  waves.  The 
rolling  diminished,  a  certain  amount  of  pitching  taking 
its  place.  Our  speed  had  fallen  from  eleven  knots  to  two. 
I  went  again  to  bed.  After  a  space  of  calm,  when  we 
seemed  crossing  the  vortex  of  a  storm,  heavy  tossing  re- 
commenced. I  was  afraid  to  allow  myself  to  fall  asleep, 
as  my  berth  was  high,  and  to  be  pitched  out  of  it  might 
be  attended  with  bruises,  if  not  with  fractures.  From 
Friday  at  noon  to  Saturday  at  noon  we  accomplished  sixty- 
six  miles,  or  an  average  of  less  than  three  miles  an  hour. 
I  overheard  the  sailors  talking  about  this  storm.  The 
'  Urgent,'  according  to  those  that  knew  her,  had  never 
previously  experienced  anything  like  it.1 

1  There  is,  it  will  be  seen,  a  fair  agreement  between  these  impressions 
and  those  so  vigorously  described  by  a  scientific  correspondent  of  the 
'Times.' 


VOYAGE   TO   ALGERIA.  191 

All  through  Saturday  the  wind,  though  somewhat 
sobered,  blew  dead  against  us.  The  atmospheric  effects 
were  exceedingly  fine.  The  cumuli  resembled  mountains 
in  shape,  and  their  peaked  summits  shone  as  white  as 
Alpine  snows.  At  one  place  this  resemblance  was  greatly 
strengthened  by  a  vast  ai'ea  of  cloud,  uniformly.illuminated, 
and  lying  like  a  n&ve  below  the  peaks.  From  it  fell  a 
kind  of  cloud-river  strikingly  like  a  glacier.  The  horizon 
at  sunset  was  remarkable — spaces  of  brilliant  green  between 
clouds  of  fiery  red.  Eainbows  had  been  frequent  through- 
out the  day,  and  at  night  a  perfectly  continuous  lunar 
bow  spanned  the  heavens  from  side  to  side.  Its  colours 
were  feeble ;  but,  contrasted  with  the  black  ground  against 
which  it  rested,  its  luminousness  was  extraordinary. 

Sunday  morning  found  us  opposite  to  Lisbon,  and  at 
midnight  we  rounded  Cape  St.  Vincent,  where  the  lurch- 
ing seemed  disposed  to  recommence.  Through  the  kind- 
ness of  Lieutenant  Walton,  a  cot  had  been  slung  for  me. 
It  hung  between  a  tiller-wheel  and  a  flue,  and  at  one  A.M. 
I  was  roused  by  the  banging  of  the  cot  against  its  boun- 
daries. But  the  wind  was  now  behind  us,  and  we  went 
along  at  a  speed  of  eleven  knots.  We  felt  certain  of 
reaching  Cadiz  by  three.  But  a  new  lighthouse  came  in 
sight,  which  some  affirmed  to  be  Cadiz  Lighthouse,  while 
the  surrounding  houses  were  declared  to  be  Cadiz  itself. 
Out  of  deference  to  these  statements,  the  navigating 
lieutenant  changed  his  course,  and  steered  for  the  place. 
A  pilot  came  on  board,  and  he  informed  us  that  we  were 
before  the  mouth  of  the  Guadalquivir,  and  that  the  light- 
house was  that  of  Cipiona.  Cadiz  was  still  some  eighteen 
miles  distant. 

We  steered  towards  the  city,  hoping  to  get  into  the 
harbour  before  dark.  But  the  pilot  was  snapped  up  by 
another  vessel,  and  we  did  not  get  in.  We  beat  about 
during  the  night,  and  in  the  morning  found  ourselves 


192  FRAGMENTS    OP   SCIENCE. 

about  fifteen  miles  from  Cadiz.  The  sun  rose  behind  the 
city,  and  we  steered  straight  into  the  light.  The  three- 
towered  cathedral  stood  in  the  midst-,  round  which 
swarmed  apparently  a  multitude  of  chimney-stacks.  A 
nearer  approach  showed  the  chimneys  to  be  small  turrets. 
A  pilot  was  taken  on  board  ;  for  there  is  a  dangerous 
shoal  in  the  harbour.  The  appearance  of  the  town  as  the 
sun  shone  upon  its  white  and  lofty  walls  was  singularly 
beautiful.  We  cast  anchor ;  some  officials  arrived  and 
demanded  a  clean  bill  of  health.  We  had  none.  They 
would  have  nothing  to  do  with  us  ;  so  the  yellow  quaran- 
tine flag  was  hoisted,  and  we  waited  for  permission  to  land 
the  Cadiz  party.  After  some  hours'  delay  the  English 
consul  and  vice-consul  came  on  board,  and  with  them  a 
Spanish  officer  ablaze  with  gold  lace  and  decorations. 
Under  slight  pressure  the  requisite  permission  had  been 
granted.  We  landed  our  party,  and  in  the  afternoon 
weighed  anchor.  Thanks  to  the  kindness  of  our  excellent 
paymaster,  I  was  here  transferred  to  a  roomier  berth. 

Cadiz  soon  sank  beneath  the  sea,  and  we  sighted  in 
succession  Cape  Trafalgar,  Tarifa,  and  the  revolving  light 
of  Ceuta.  The  water  was  very  calm,  and  the  moon  rose 
in  a  quiet  heaven.  She  swung  with  her  convex  surface 
downwards,  the  common  boundary  between  light  and 
shadow  being  almost  horizontal.  A  pillar  of  reflected 
light  shimmered  up  to  us  from  the  slightly  rippled  sea. 
1  had  previously  noticed  the  phosphorescence  of  the  water, 
but  to-night  it  was  stronger  than  usual,  especially  among 
the  foam  at  the  bows.  A  bucket  let  down  into  the  sea 
brought  up  a  number  of  the  little  sparkling  organisms 
which  caused  the  phosphorescence.  I  caught  some  of  them 
in  my  hand.  And  here  an  appearance  was  observed  which 
was  new  to  most  of  iis,  and  strikingly  beautiful  to  all. 
Standing  at  the  bow  and  looking  forwards,  at  a  distance 
of  forty  or  fifty  yards  from  the  ship,  a  number  of  luminous 


VOYAGE   TO   ALGERIA.  193 

streamers  were  seen  rushing  towards  us.  On  nearing  the 
vessel  they  rapidly  turned,  like  a  comet  round  its  peri- 
helion, placed  themselves  side  by  side,  and,  in  parallel 
trails  of  light,  kept  up  with  the  ship.  One  of  them  placed 
itself  right  in  front  of  the  bow  as  a  pioneer.  These  comets 
of  the  sea  were  joined  at  intervals  by  others.  Sometimes 
as  many  as  six  at  a  time  would  rush  at  us,  bend  with  extra- 
ordinary rapidity  round  a  sharp  curve,  and  afterwards 
keep  us  company.  I  leaned  over  the  bow,  and  scanned 
the  streamers  closely.  The  frontal  portion  of  each  of 
them  revealed  the  outline  of  a  porpoise.  The  rush  of 
the  creatures  through  the  water  had  started  the  phospho- 
rescence, every  spark  of  which  was  converted  by  the 
motion  of  the  retina  into  a  line  of  light.  Each  porpoise 
was  thus  wrapped  in  a  luminous  sheath.  The  phospho- 
rescence did  not  cease  at  the  creature's  tail,  but  was 
carried  many  porpoise-lengths  behind  it. 

To  our  right  we  had  the  African  hills,  illuminated  by 
the  moon.  Gibraltar  Eock  at  length  became  visible,  but 
the  town  remained  long  hidden  by  a  belt  of  haze.  Through 
this  at  length  the  brighter  lamps  struggled.  It  was  like 
the  gradual  resolution  of  a  nebula  into  stars.  As  the  in- 
tervening depth  became  gradually  less,  the  mist  vanished 
more  and  more,  and  finally  all  the  lamps  shone  through 
it.  They  formed  a  bright  foil  to  the  sombre  mass  of  rock 
above  them.  The  sea  was  so  calm  and  the  scene  so  lovely 
that  Mr.  Huggins  and  myself  stayed  on  deck  till  the  ship 
was  moored,  near  midnight.  During  our  walking  to  and 
fro  a  striking  enlargement  of  the  disk  of  Jupiter  was  ob- 
served, whenever  the  heated  air  of  the  funnel  came  be- 
tween us  and  the  planet.  On  passing  away  from  the 
heated  air,  the  flat  dim  disk  would  immediately  shrink  to  a 
luminous  point.  The  effect  was  one  of  visual  persistence. 
The  retinal  image  of  the  planet  was  set  quivering  in 
all  azimuths  by  the  streams  of  heated  air,  describing  in 


194  FRAGMENTS    OP   SCIENCE. 

quick  succession  minute  lines  of  light,  which  summed 
themselves  to  a  disk  of  sensible  area. 

At  six  o'clock  next  morning,  the  gun  at  the  Signal 
Station  on  the  summit  of  the  rock,  boomed.  At  eight  the 
band  on  board  the  i  Trafalgar '  training-ship,  which  was 
in  the  harbour,  struck  up  the  national  anthem ;  and  im- 
mediately afterwards  a  crowd  of  mite  like  cadets  swarmed 
up  the  rigging.  After  the  removal  of  the  apparatus 
belonging  to  the  Gibraltar  party  we  went  on  shore. 
Winter  was  in  England  when  we  left,  but  here  we  had  the 
warmth  of  summer.  The  vegetation  was  luxuriant — palm- 
trees,  cactuses,  and  aloes,  all  ablaze  with  scarlet  flowers. 
A  visit  to  the  Governor  was  proposed,  as  an  act  of  necessary 
courtesy,  and  I  accompanied  Admiral  Ommaney  and  Mr. 
Huggins  to  '  the  Convent,'  or  Government  House.  We 
sent  in  our  cards,  waited  for  a  time,  and  were  then  con- 
ducted by  an  orderly  to  his  Excellency.  He  is  a  fine  old 
man,  over  six  feet  high,  and  of  frank  military  bearing. 
He  received  us  and  conversed  with  us  in  a  very  genial 
manner.  He  took  us  to  see  his  garden,  his  palms,  his 
shaded  promenades,  and  his  orange-trees  loaded  with  fruit, 
in  all  of  which  he  took  manifest  delight.  Evidently  '  the 
hero  of  Kars'  had  fallen  upon  quarters  after  his  own 
heart.  He  appeared  full  of  good  nature,  and  engaged  us 
on  the  spot  to  dine  with  him  that  day. 

We  sought  the  town-major  for  a  pass  to  visit  the  lines. 
While  awaiting  his  arrival  I  purchased  a  stock  of  white 
glass  bottles,  with  a  view  to  experiments  on  the  colour  of 
the  sea.  Mr.  Huggins  and  myself,  who  wished  to  see  the 
rock,  were  taken  by  Captain  Salmond  to  the  library,  where 
a  model  of  Gibraltar  is  kept,  and  where  we  had  a  capital 
preliminary  lesson.  At  the  library  we  met  Colonel 
Maberly,  a  courteous  and  kindly  man,  who  gave  us  good 
advice  regarding  our  excursion.  He  sent  an  orderly  with 
us  to  the  entrance  of  the  lines.  The  orderly  handed  us 
over  to  an  intelligent  Irishman,  who  was  directed  to  show 


VOYAGE   TO   ALGERIA.  195 

us  everything  that  we  desired  to  see,  and  to  hide  nothing 
from  us.  We  took  the  '  upper  line,'  traversed  the  galleries 
hewn  through  the  limestone;  looked  through  the  embra- 
sures, which  opened  like  doors  in  the  precipice,  towards 
the  hills  of  Spain ;  reached  St.  George's  Hall,  and  went 
still  higher,  emerging  on  the  summit  of  one  of  the  noblest 
cliffs  I  have  ever  seen. 

Beyond  were  the  Spanish  lines,  marked  by  a  line  of 
white  sentry-boxes ;  nearer  were  the  English  lines,  less 
conspicuously  indicated  ;  and  between  both  was  neutral 
ground.  Behind  the  Spanish  lines  rose  the  conical  hill 
called  the  Queen  of  Spain's  Chair.  The  general  aspect  of 
Spain  from  the  rock  is  bold  and  rugged.  Doubling  back 
from  the  galleries,  we  struck  upwards  towards  the  crest, 
reached  the  Signal  Station,  where  we  indulged  in  '  shandy- 
gaff '  and  bread  and  cheese.  Thence  to  O'Hara's  Tower, 
the  highest  point  of  the  rock.  It  was  built  by  a  former 
Governor,  who,  forgetful  of  the  laws  of  terrestrial  curva- 
ture, thought  he  might  look  from  the  tower  into  the  port 
of  Cadiz.  The  tower  is  riven,  and  it  may  be  climbed  along 
the  edges  of  the  crack.  We  got  to  the  top  of  it ;  thence 
descended  the  curious  Mediterranean  Stair — a  zigzag, 
mostly  of  steps  down  a  steeply  falling  slope,  amid  palmetto 
brush,  aloes,  and  prickly  pear. 

Passing  over  the  Windmill  Hill,  we  were  joined  at  the 
'  Governor's  Cottage '  by  a  car,  and  drove  afterwards  to 
the  lighthouse  at  Europa  Point.  The  tower  was  built,  I 
believe,  by  Queen  Adelaide,  and  it  contains  a  fine  dioptric 
apparatus  of  the  first  order,  constructed  by  Messrs.  Chance, 
of  Birmingham.  At  the  appointed  hour  we  were  at  the 
Convent.  During  dinner  the  same  genial  traits  which 
appeared  in  the  morning  were  still  more  conspicuous. 
The  freshness  of  the  Governor's  nature  showed  itself  best 
when  he  spoke  of  his  old  antagonist  in  arms,  MouraviefF. 
Chivalry  in  war  is  consistent  with  its  stern  prosecution, 
11 


196  FRAGMENTS    OF   SCIENCE. 

These  two  men  were  chivalrous,  and  after  striking  the 
last  blow  became  friends  for  ever.  Our  kind  and  cour- 
teous reception  at  Gibraltar  is  a  thing  to  be  remembered 
with  pleasure. 

On  December  15  we  committed  ourselves  to  the 
Mediterranean.  The  views  of  Gibraltar  with  which  we 
are  most  acquainted  represent  it  as  a  huge  ridge ;  but 
its  aspect,  end  on,  both  from  the  Spanish  lines  and  from 
the  other  side,  is  truly  noble.  There  is  a  sloping  bank  of 
sand  at  the  back  of  the  rock,  which  I  was  disposed  to 
regard  simply  as  the  debris  of  the  limestone.  I  wished 
to  let  myself  down  upon  it,  but  had  not  the  time.  My 
friend  Mr.  Busk,  however,  assures  me  that  it  is  silica,  and 
that  the  same  sand  constitutes  the  adjacent  neutral  ground. 
There  are  theories  afloat  as  to  its  having  been  blown  from 
Sahara.  The  Mediterranean  throughout  this  first  day, 
and  indeed  throughout  the  entire  voyage  to  Oran,  was  of 
a  less  deep  blue  than  the  Atlantic.  Possibly  the  quantity 
of  organisms  may  have  modified  the  colour.  At  night 
the  phosphorescence  was  startling,  breaking  with  the 
suddenness  of  a  snapped  spring  along  the  crests  of  the 
waves  formed  by  the  port  and  starboard  bows.  Its  strength 
was  not  uniform.  Having  flashed  brilliantly  for  a  time,  it 
would  in  part  subside,  and  afterwards  regain  its  vigour. 
Several  large  phosphorescent  masses  of  weird  appearance 
also  floated  past. 

On  the  morning  of  the  16th  we  sighted  the  fort  and 
lighthouse  of  Marsa  el  Kibir,  and  beyond  them  the  white 
walls  of  Oran  lying  in  the  bight  of  a  bay,  sheltered  by 
dominant  hills.  The  sun  was  shining  brightly ;  during 
our  whole  voyage  we  had  not  had  so  fine  a  day.  The 
wisdom  which  had  led  us  to  choose  Oran  as  our  place  of 
observation  seemed  demonstrated.  A  rather  excitable 
pilot  came  on  board,  and  he  guided  us  in  behind  the  Mole, 
which  had  suffered  much  damage  "last  year  from  an  unex 


VOYAGE   TO  ALGERIA.  197 

plained  outburst  of  waves  from  the  Mediterranean.  Both 
port  and  bow  anchors  were  cast  in  deep  water.  With 
three  huge  hawsers  the  ship's  stern  was  made  fast  to  three 
gun-pillars  fixed  in  the  Mole ;  and  here  for  a  time  the 
'  Urgent '  rested  from  her  labours. 

M.  Janssen,  who  had  rendered  his  name  celebrated  by 
his  observations  of  the  eclipse  in  India  in  1868,  when  he 
showed  the  solar  flames  to  be  eruptions  of  incandescent 
hydrogen,  was  already  encamped  in  the  open  country 
about  eight  miles  from  Oran.  On  December  2  he  had 
quitted  Paris  in  a  balloon,  with  a  strong  young  tailor 
as  his  assistant,  had  descended  near  the  mouth  of  the 
Loire,  seen  M.  Gambetta,  and  received  from  him  en- 
couragement and  aid.  On  the  day  of  our  arrival  his  en- 
campment was  visited  by  Mr.  Huggins,  and  the  kind  and 
courteous  Engineer  of  the  Port  drove  me  subsequently,  in 
his  own  phaeton,  to  the  place.  It  bore  the  best  repute  as 
regards  freedom  from  haze  and  fog,  and  commanded  an 
open  outlook  ;  but  it  was  inconvenient  for  us  on  account 
of  its  distance  from  the  ship.  The  place  next  in  repute  was 
the  railway  station,  between  two  and  three  miles  distant 
from  the  Mole.  It  was  inspected,  but,  being  enclosed, 
was  abandoned  for  an  eminence  in  an  adjacent  garden,  the 
property  of  Mr.  Hinshelwood,  a  Scotchman  who  had 
settled  some  years  previously  as  an  Esparto  merchant 
in  Oran.1  He,  in  the  most  liberal  manner,  placed  his 
ground  at  the  disposition  of  the  party.  Here  the  tents 
were  pitched,  on  the  Saturday,  by  Captain  Salmond  and 
his  intelligent  corps  of  sappers,  the  instruments  being 
erected  on  the  Monday  under  cover  of  the  tents. 

Close  to  the  railway  station  runs  a  new  loopholed  wall 
of  defence,  through  which  the  highway  passes  into  the 
open  country.  Standing  on  the  highway,  and  looking 

1  Esparto  is  a  kind  of  grass  now  much  used  in  the  manufacture  of  paper, 


198  FRAGMENTS   OP  SCIENCE. 

southwards,  about  twenty  yards  to  the  right  is  a  small 
bastionet,  intended  to  carry  a  gun  or  two.  Its  roof  I 
thought  would  form  an  admirable  basis  for  my  telescope, 
while  the  view  of  the  surrounding  country  was  unimpeded 
in  all  directions.  The  authorities  kindly  allowed  me  the 
use  of  this  bastionet.  Two  men,  one  a  blue-jacket  named 
Elliot,  and  the  other  a  marine  named  Hill,  were  placed  at 
my  disposal  by  Lieutenant  "Walton ;  and,  thus  aided,  on 
Monday  morning  I  mounted  my  telescope.  The  instru- 
ment was  new  to  me,  and  some  hours  of  discipline  were 
spent  in  mastering  all  the  details  of  its  manipulation. 

Mr.  Huggins  joined  me,  and  we  visited  together  the 
Arab  quarter  of  Oran.  The  flat-roofed  houses  appeared 
very  clean  and  white.  The  street  was  filled  with  loiterers, 
and  the  thresholds  were  occupied  by  picturesque  groups. 
Some  of  the  men  were  very  fine.  We  saw  many  straight, 
manly  fellows  who  must  have  been  six  feet  four  in  height. 
They  passed  us  with  perfect  indifference,  evincing  no 
anger,  suspicion,  or  curiosity,  hardly  caring  in  fact  to 
glance  at  us  as  we  passed.  In  one  instance  only  during 
my  stay  at  Oran  was  I  spoken  to  by  an  Arab.  He  was  a 
tall,  good-humoured  fellow,  who  came  smiling  up  to  me, 
and  muttered  something  about  '  les  Anglais.'  The  mixed 
population  of  Oran  is  picturesque  in  the  highest  degree : 
the  Jews,  rich  and  poor,  varying  in  their  costumes  as  their 
wealth  varies  ;  the  Arabs  more  picturesque  still,  and  of  all 
shades  of  complexion — the  negroes,  the  Spaniards,  the 
French,  all  grouped  together,  and  each  preserving  their 
own  individuality,  formed  a  picture  intensely  interesting 
to  me. 

On  Tuesday,  the  20th,  I  was  early  at  the  bastionet. 
The  night  had  been  very  squally.  The  sergeant  of  the 
sappers  took  charge  of  our  key,  and  on  Tuesday  morning 
Elliot  went  for  it.  He  brought  back  the  intelligence  that 
the  tents  had  been  blown  down,  and  the  instruments  over- 


VOYAGE   TO  ALGERIA.  199 

turned.  Among  these  was  a  large  and  valuable  equato- 
rial from  the  Royal  Observatory,  Greenwich.  It  seemed 
hardly  possible  that  this  instrument,  with  its  wheels  and 
verniers  and  delicate  adjustments,  could  have  escaped 
uninjured  from  such  a  fall.  This,  however,  was  the  case; 
and  during  the  day  all  the  overturned  instruments  were 
restored  to  their  places,  and  found  to  be  in  practical 
working  order.  This  and  the  following  day  were  devoted 
to  incessant  schooling.  I  had  come  out  as  a  general  star- 
gazer,  and  not  with  the  intention  of  devoting  myself  to 
the  observation  of  any  particular  phenomenon.  I  wished 
to  see  the  whole — the  first  contact,  the  advance  of  the 
moon,  and  the  successive  swallowing  up  of  the  solar  spots, 
the  breaking  of  the  last  line  of  crescent  by  the  lunar 
mountains  into  Bailey's  beads,  the  advance  of  the  shadow 
through  the  air,  the  appearance  of  the  corona  and  pro- 
minences at  the  moment  of  totality,  the  radiant  streamers 
of  the  corona,  the  internal  structure  of  the  flames,  a  glance 
through  a  polariscope,  a  sweep  round  the  landscape  with 
the  naked  eye,  the  reappearance  of  the  solar  limb  through 
Bailey's  beads,  and,  finally,  the  retreat  of  the  lunar 
shadow  through  the  air. 

I  was  provided  with  a  telescope  of  admirable  definition, 
mounted,  adjusted,  packed,  and  most  liberally  placed  at 
my  disposal  by  Mr.  Warren  De  La  Rue.  The  telescope 
grasped  the  whole  of  the  sun,  and  a  considerable  portion  of 
the  space  surrounding  it.  But  it  would  not  take  in  the 
extreme  limits  of  the  corona.  For  this  I  had  lashed  on 
to  the  large  telescope  a  light  but  powerful  instrument, 
constructed  by  Ross,  and  lent  to  me  by  Mr.  Huggins.  I 
was  also  furnished  with  an  excellent  binocular  by  Mr. 
Dallmeyer.  In  fact,  no  man  could  have  been  more 
efficiently  supported.  It  required  a  strict  parcelling  out 
of  the  interval  of  totality  to  embrace  in  it  Ihe  entire 
series  of  observations.  These,  while  the  sun  remained 


200  FRAGMENTS    OF   SCIENCE. 

visible,  were  to  be  made  with  an  unsilvered  diagonal  eye- 
piece, which  reflected  but  a  small  fraction  of  the  sun'a 
light,  this  fraction  being  still  further  toned  down  by  a 
dark  glass.  At  the  moment  of  totality  the  dark  glass 
was  to  be  removed,  and  a  silver  reflector  pushed  in,  so  as 
to  get  the  maximum  of  light  from  the  corona  and  pro- 
minences. The  time  of  totality  was  distributed  as  fol- 
lows : 

1.  Observe  approach  of  shadow  through  the  air:  totality. 

2.  Telescope     .         .         .         .30  seconds. 

3.  Finder         ....     30  seconds. 

4.  Double  image  prism     .         .15  seconds. 

5.  Naked  eye  .        .        .        .10  seconds. 

6.  Finder  or  binocular      .         .     20  seconds. 

7.  Telescope    .        .        .        .20  seconds. 

8.  Observe  retreat  of  shadow. 

In  our  rehearsals  Elliot  stood  beside  me,  watch  in 
hand,  and  furnished  with  a  lantern.  He  called  out  at  the 
end  of  each  interval,  while  I  moved  from  telescope  to 
finder,  from  finder  to  polariscope,  from  polariscope  to 
naked  eye,  from  naked  eye  back  to  finder,  from  finder  to 
telescope,  abandoning  the  instrument  finally  to  observe 
the  retreating  shadow.  All  this  we  went  over  twenty 
times,  while  looking  at  the  actual  sun,  and  keeping  him 
in  the  middle  of  the  field.  It  was  my  object  to  render 
the  repetition  of  the  lesson  so  mechanical  as  to  leave  no 
room  for  flurry,  forgetfulness,  or  excitement.  Volition 
was  not  to  be  called  upon,  nor  judgment  exercised,  but  a 
well-beaten  path  of  routine  was  to  be  followed.  Had  the 
opportunity  occurred,  I  think  the  programme  would  have 
been  strictly  carried  out. 

But  the  opportunity  did  not  occur.  For  several  days 
the  weather  had  been  ill-natured.  "We  had  wind  so  strong 
as  to  render  the  hawsers  at  the  stern  of  the  '  Urgent '  as 
rigid  as  iron,  and  to  destroy  the  navigating  lieutenant's 
sleep.  "We  had  clouds,  a  thunder-storm,  and  some  rain. 


VOYAGE   TO  ALGERIA.  201 

Still  the  hope  was  held  out  that  the  atmosphere  would 
cleanse  itself,  and  if  it  did  we  were  promised  air  of 
extraordinary  limpidity.  Early  on  the  22nd  we  were 
all  at  our  posts.  Spaces  of  blue  in  the  early  morning 
gave  us  some  encouragement,  but  all  depended  on  the  re- 
lation of  these  spaces  to  the  surrounding  clouds.  Which 
of  them  were  to  grow  as  the  day  advanced  ?  The  wind 
was  high,  and  to  secure  the  steadiness  of  my  instrument 
I  was  forced  to  retreat  behind  a  projection  of  the  bastionet, 
place  stones  upon  its  stand,  and,  further,  to  avail  myself 
of  the  shelter  of  a  sail.  My  practised  men  fastened  the 
Bail  at  the  top,  and  loaded  it  with  boulders  at  the  bottom. 
It  was  tried  severely,  but  it  stood  firm. 

The  clouds  and  blue  spaces  fought  for  a  time  with 
varying  success.  The  sun  was  hidden  and  revealed  at  in- 
tervals, hope  oscillating  in  synchronism  with  the  changes 
of  the  sky.  At  the  moment  of  first  contact  a  dense  cloud 
intervened;  but  a  minute  or  two  afterwards  the  cloud 
had  passed,  and  the  encroachment  of  the  black  body  of 
the  moon  was  evident  upon  the  solar  disk.  The  moon 
marched  onward,  and  I  saw  it  at  frequent  intervals  ;  a 
large  group  of  spots  were  approached  and  swallowed  up. 
Subsequently  I  caught  sight  of  the  lunar  limb  as  it  cut 
through  the  middle  of  a  large  spot.  The  spot  was  not  to 
be  distinguished  from  the  moon,  but  rose  like  a  mountain 
above  it.  The  clouds,  when  thin,  could  be  seen  as  grey 
scud  drifting  across  the  black  surface  of  the  moon  ;  but 
they  thickened  more  and  more,  and  made  the  intervals  of 
clearness  scantier.  During  these  moments  I  watched  with 
an  interest  bordering  upon  fascination  the  march  of  the 
silver  sickle  of  the  sun  across  the  field  of  the  telescope. 
It  was  so  sharp  and  so  beautiful.  No  trace  of  the  lunar 
limb  could  be  observed  beyond  the  sun's  boundary.  Here, 
indeed,  it  could  only  be  relieved  by  the  corona,  which 
was  utterly  cut  off  by  the  dark  glass.  The  blackness  of 


202  FRAGMENTS   OF   SCIENCE. 

the  moon  beyond  the  sun  was,  in  fact,  confounded  with 
the  blackness  of  space. 

Beside  me  was  Elliot  with  the  watch  and  lantern,  while 
Lieutenant  Archer,  of  the  Koyal  Engineers,  had  the  kind- 
ness to  take  charge  of  my  note-book.  I  mentioned,  and 
he  wrote  rapidly  down,  such  things  as  seemed  worthy  of 
remembrance.  Thus  my  hands  and  mind  were  entirely 
free  ;  but  it  was  all  to  no  purpose.  A  patch  of  sunlight  fell 
and  rested  upon  the  landscape  some  miles  away.  It 
was  the  only  illuminated  spot  within  view.  But  to  the 
north-west  there  was  still  a  space  of  blue  which  might 
reach  us  in  time.  Within  seven  minutes  of  totality  an- 
other space  towards  the  zenith  became  very  dark.  The 
atmosphere  was,  as  it  were,  on  the  brink  of  a  preci- 
pice ;  it  was  charged  with  humidity,  which  required  but 
a  slight  chill  to  bring  it  down  in  clouds.  This  was  fur- 
nished by  the  withdrawal  of  the  solar  beams ;  the  clouds 
did  come  down,  covering  up  the  space  of  blue  on  which 
our  hopes  had  so  long  rested.  I  abandoned  the  telescope 
and  walked  to  and  fro,  like  a  caged  leopard.  As  the 
moment  of  totality  approached,  the  descent  towards 
darkness  was  as  obvious  as  a  falling  stone.  I  looked 
towards  a  distant  ridge,  where  the  darkness  would  first 
appear.  At  the  moment  a  fan  of  beams,  issuing  from  the 
hidden  sun,  was  spread  out  over  the  southern  heavens. 
These  beams  are  bars  of  alternate  light  and  shade,  pro- 
duced in  illuminated  haze  by  the  shadows  of  floating 
cloudlets  of  varying  density.  The  beams  are  practically 
parallel,  but  by  an  effect  of  perspective  they  appear  diver- 
gent, having  the  sun,  in  fact,  for  their  point  of  converg- 
ence. The  darkness  took  possession  of  the  ridge  referred 
to,  lowered  upon  M.  Janssen's  observatory,  passed  over  the 
southern  heavens,  blotting  out  the  beams  as  if  a  sponge 
had  been  drawn  across  them.  It  then  took  possession  of 
three  spaces  of  blue  sky  in  the  south-eastern  atmosphere. 


VOYAGE   TO   ALGERIA.  203 

I  again  looked  towards  the  ridge.  A  glimmer  as  of  day- 
dawn  was  behind  it,  and  immediately  afterwards  the  fan 
of  beams,  which  had  been  for  more  than  two  minutes 
absent,  revived.  The  eclipse  of  1870  had  ended,  and,  as 
far  as  the  corona  was  concerned,  we  had  been  defeated. 

Even  in  the  heart  of  the  eclipse  the  darkness  was  by 
no  means  perfect.  Small  print  could  be  read.  In  fact, 
the  clouds  which  rendered  the  day  a  dark  one,  by  scat- 
tering light  into  the  shadow,  rendered  the  darkness  less 
intense  than  it  would  have  been  had  the  atmosphere  been 
without  cloud.  In  the  more  open  spaces  I  sought  for 
stars,  but  could  find  none.  There  was  a  lull  in  the  wind 
before  and  after  totality,  but  during  the  totality  the 
wind  was  strong.  I  waited  for  some  time  on  the  bastionet, 
hoping  to  get  a  glimpse  of  the  moon  on  the  opposite 
border  of  the  sun,  but  in  vain.  The  clouds  continued, 
and  some  rain  fell.  The  day  brightened  somewhat  after- 
wards, and,  having  packed  all  up,  in  the  sober  twilight 
Mr.  Crookes  and  myself  climbed  the  heights  above  the 
fort  of  Vera  Cruz.  From  this  eminence  we  had  a  very 
noble  view  over  the  Mediterranean  and  the  flanking 
African  hills.  The  sunset  was  remarkable,  and  the  whole 
outlook  exceedingly  fine. 

The  able  and  well-instructed  medical  officer  of  the 
1  Urgent,'  Mr.  Goodman,  observed  the  following  tempera- 
tures during  the  progress  of  the  eclipse : 

Hour  Dpg.  Hour  Deg. 

11.45  .  .  56  12.43  .         .  51 

11.55  .  55  1.5  ..  52 

12.10  .  .  54  1.27  .         .  53 

12.37  .  .  53  1.44  .         .  56 

12.39  .  .  52  2.10  .         .  57 

The  minimum  temperature  occurred  some  minutes  after 
totality,  when  a  slight  rain  fell. 

The  wind  was  so  strong  on  the  23rd  that  Captain 
Henderson  would  not  venture  out.  Guided  by  Mr. 


204  FRAGMENTS   OP   SCIENCE. 

Goodman,  I  visited  a  cave  scooped  into  a  remarkable 
stratum  of  shell-breccia,  and,  thanks  to  my  guide,  secured 
specimens.  Mr.  Busk  informs  me  that  a  precisely  similar 
breccia  is  found  at  Gibraltar,  at  approximately  the  same 
level.  During  the  afternoon,  Admiral  Ommaney  and 
myself  drove  to  the  fort  of  Marsa  el  Kibir.  The  forti- 
fication is  of  ancient  origin,  the  Moorish  arches  being  still 
there  in  decay,  but  the  fort  is  now  very  strong.  About 
four  or  five  hundred  fine-looking  dragoons  were  looking 
after  their  horses,  waiting  for  a  lull  to  enable  them  to 
embark  for  France.  One  of  their  officers  was  wander- 
ing in  a  very  solitary  fashion  over  the  fort.  We  had 
some  conversation  with  him.  He  had  been  at  Sedan, 
had  been  taken  prisoner,  but  had  effected  his  escape.  He 
shook  his  head  when  we  spoke  of  the  termination  of  the 
war,  and  predicted  its  long  continuance.  There  was 
bitterness  in  his  tone  as  he  spoke  of  the  charges  of  treason 
so  lightly  levelled  against  French  commanders.  The  green 
waves  raved  round  the  promontory  on  which  the  fort 
stands,  smiting  the  rocks,  breaking  into  foam,  and  jump- 
ing, after  impact,  to  a  height  of  a  hundred  feet  and  more 
into  the  air.  On  our  return  our  vehicle  broke  down 
through  the  loss  of  a  wheel.  The  Admiral  went  on  board, 
while  I  hung  long  over  the  agitated  sea.  The  little 
horses  of  Oran  well  merit  a  passing  word.  Their  speed 
and  endurance,  which  are  both  heavily  drawn  upon  by 
their  drivers,  are  extraordinary. 

The  wind  sinking,  we  lifted  anchor  on  the  24th.  For 
some  hours  we  went  pleasantly  along;  but  during  the 
afternoon  the  storm  revived,  and  it  blew  heavily  against 
us  all  the  night.  When  we  came  opposite  the  Bay  of 
Almeria,  on  the  25th,  the  captain  turned  the  ship,  and 
steered  into  the  bay,  where,  under  the  shadow  of  the 
Sierra  Nevada,  we  passed  Christmas  night  in  peace.  Next 
morning  '  a  rose  of  dawn  '  rested  on  the  snows  of  the  ad- 


VOYAGE   TO  ALGERIA.  205 

jacent  mountains,  while  a  purple  haze  was  spread  over  the 
lower  hills.  I  had  no  notion  that  Spain  possessed  so  fine 
a  range  of  mountains  as  the  Sierra  Nevada.  The  height 
is  considerable,  but  the  form  also  is  such  as  to  get  the 
maximum  of  grandeur  out  of  the  height.  We  weighed 
anchor  at  eight  A.M.,  passing  for  a  time  through  shoal 
water,  the  bottom  having  been  evidently  stirred  up.  The 
adjacent  land  seemed  eroded  in  a  remarkable  manner. 
It  has  its  floods,  which  excavate  these  valleys  and  ravines, 
and  leave  those  singular  ridges  behind.  Towards  evening 
I  climbed  the  mainmast,  and,  standing  on  the  cross-trees, 
saw  the  sun  set  amid  a  blaze  of  fiery  clouds.  The  wind 
was  strong  and  bitterly  cold,  and  I  was  glad  to  slide  to 
the  deck  along  a  rope,  which  stretched  from  the  mast-head 
to  the  ship's  side.  That  night  we  cast  anchor  beside  the 
Mole  of  Gibraltar. 

On  the  morning  of  the  27th,  in  company  with  two 
friends,  I  drove  to  the  Spanish  lines,  with  the  view  of  seeing 
the  rock  from  that  side.  It  is  an  exceedingly  noble  mass. 
The  Peninsular  and  Oriental  mail-boat  had  been  sig- 
nalled and  had  come.  Heavy  duties  called  me  homeward, 
and  by  transferring  myself  from  the  '  Urgent'  to  the  mail- 
steamer  I  should  gain  three  days.  I  hired  a  boat,  rowed 
to  the  steamer,  learned  that  she  was  to  start  at  one,  and 
returned  with  all  speed  to  the  '  Urgent.'  Making  known 
to  Captain  Henderson  my  wish  to  get  away,  he  expressed 
doubts  as  to  the  possibility  of  reaching  the  mail-steamer 
in  time.  With  his  accustomed  kindness,  he,  however, 
placed  a  boat  at  my  disposal.  Four  hardy  fellows  and  one 
of  the  ship's  officers  jumped  into  it ;  my  luggage,  hastily 
thrown  together,  was  tumbled  in  afterwards,  and  we  were 
immediately  on  our  way.  We  had  nearly  four  miles  to 
row  in  about  twenty  minutes  ;  but  we  hoped  the  mail- 
boat  might  not  be  punctual.  For  a  time  we  watched  her 
anxiously;  there  was  no  motion;  we  came  nearer,  but  the 


206  FRAGMENTS   OP   SCIENCE. 

flags  were  not  yet  hauled  in.  Tiie  men  put  forth  all 
their  strength,  animated  by  the  exhortations  of  the  officer 
at  the  helm.  The  roughness  of  the  sea  rendered  their 
efforts  to  some  extent  nugatory :  still  we  were  rapidly  ap- 
proaching the  steamer.  At  length  she  moved,  punctual 
almost  to  the  minute,  at  first  slowly,  but  soon  with  quick- 
ened pace.  We  turned  to  the  left,  so  as  to  cut  across  her 
bows.  Five  minutes'  pull  would  have  brought  us  up  to 
her.  The  officer  waved  his  cap  and  I  my  hat.  '  If  they 
could  only  see  us,  they  might  back  to  us  in  a  moment.' 
But  they  did  not  see  us,  or  if  they  did,  they  paid  no  at- 
tention to  us.  I  returned  to  the  '  Urgent,'  discomfited, 
but  grateful  to  the  fine  fellows  who  had  wrought  so  hard 
to  carry  out  my  wishes. 

Glad  of  the  quiet,  in  the  sober  afternoon  I  took  a  walk 
towards  Europa  Point.  The  sky  darkened  and  heavy 
squalls  passed  at  intervals.  Private  theatricals  were  at 
the  Convent,  and  the  kind  and  courteous  Governor  had 
sent  cards  to  the  eclipse  party.  I  failed  in  my  duty  in 
not  going.  St.  Michael's  Cave  is  said  to  rival,  if  it  does 
not  outrival,  the  Mammoth  Cave  of  Kentucky.  On  the 
28th  Messrs.  Crookes,  Carpenter,  and  myself,  guided  by  a 
military  policeman  who  understood  his  work,  explored  the 
cavern.  The  mouth  is  about  1,100  feet  above  the  sea. 
We  zigzagged  up  to  it,  and  first  were  led  into  an  aperture 
in  the  rock,  at  some  height  aoove  the  true  entrance  of  the 
cave.  In  this  upper  cavern  we  saw  some  tall  and  beauti- 
ful stalactite  pillars. 

The  water  drips  from  the  roof  charged  with  bicar- 
bonate of  lime.  Exposed  to  the  air,  the  carbonic  acid 
partially  escapes,  and  the  simple  carbonate  of  lime,  which 
is  hardly  at  all  soluble  in  water,  deposits  itself  as  a  solid, 
forming  stalactites  and  stalagmites.  Even  the  exposure 
of  chalk  or  limestone  water  to  the  open  air  partially 
softens  it  A  specimen  of  the  Eedbourne  wacer  exposed 


VOYAGE   TO   ALGERIA.  207 

by  Messrs.  Graham,  Miller,  and  Hofmann,  in  a  shallow 
basin,  fell  from  eighteen  degrees  to  nine  degrees  of  hard- 
ness. The  softening  process  of  Clark  is  virtually  a  has- 
tening of  the  natural  process.  Here,  however,  instead  of 
being  permitted  to  evaporate,  half  the  carbonic  acid  is 
appropriated  by  lime,  the  half  thus  taken  up,  as  well  as 
the  remaining  half,  being  precipitated.  The  solid  pre- 
cipitate is  permitted  to  sink,  and  the  clear  supernatant 
liquid  is  limpid  soft  water. 

We  returned  to  the  real  mouth  of  St.  Michael's  Cave, 
which  is  entered  by  a  wicket.  The  floor  was  somewhat 
muddy,  and  the  roof  and  walls  were  wet.  We  were 
soon  in  the  midst  of  a  natural  temple,  where  tall  columns 
sprang  complete  from  floor  to  roof,  while  incipient  columns 
were  growing  to  meet  each  other,  upwards  and  downwards. 
The  water  which  trickles  from  the  stalactite,  after  having 
in  part  yielded  up  its  carbonate  of  lime,  falls  upon  the 
floor  vertically  underneath,  and  there  builds  the  stalag- 
mite. Consequently,  the  pillars  grow  from  above  and 
below  simultaneously,  along  the  same  vertical.  It  is  easy 
to  distinguish  the  stalagmitic  from  the  stalactitic  portion 
of  the  pillars.  The  former  is  always  divided  into  short 
segments  by  protuberant  rings,  as  if  deposited  periodi- 
cally, while  the  latter  presents  a  uniform  surface.  In 
some  cases  the  points  of  inverted  cones  of  stalactite  rested 
on  the  centres  of  pillars  of  stalagmite.  The  process  of 
solidification  and  the  architecture  were  alike  beautiful. 

We  followed  our  guide  through  various  branches  and 
arms  of  the  cave,  climbed  and  descended  steps,  halted  at 
the  edges  of  dark  shafts  and  apertures,  and  squeezed  our- 
selves through  narrow  passages.  From  time  to  time  we 
halted,  while  Mr.  Crookes  illuminated  with  ignited  mag- 
nesium wire,  the  roof,  columns,  dependent  spears,  and 
graceful  drapery  of  the  stalactites.  Once,  coming  to  a 
magnificent  cluster  of  icicle-like  spears,  we  helped  our- 


208  FRAGMENTS   OF   SCIENCE. 

selves  to  specimens.  There  was  some  difficulty  in  detach- 
ing the  more  delicate  ones,  their  fragility  was  so  great. 
A  consciousness  of  vandalism,  which  smote  me  at  the 
time,  haunts  me  still ;  for,  though  our  requisitions  were 
moderate,  this  beauty  ought  not  to  be  at  all  invaded. 
Pendent  from  the  roof,  in  their  natural  habitat,  nothing 
can  exceed  their  delicate  beauty ;  they  live,  as  it  were, 
surrounded  by  organic  connections.  In  London  they  are 
curious,  but  not  beautiful.  Of  gathered  shells  Emerson 
writes : 

I  wiped  away  the  weeds  and  foam, 
And  brought  my  sea-born  treasures  home : 
But  the  poor,  unsightly,  noisome  things 
Had  left  their  beauty  on  the  shore, 
With  the  sun,  and  the  sand,  and  the  wild  uproa 

The  promontory  of  Gibraltar  is  so  burrowed  with 
caverns  that  it  has  been  called  the  Hill  of  Caves.  They 
are  apparently  related  to  the  geologic  disturbances  which 
the  rock  has  undergone.  The  earliest  of  these  is  the 
tilting  of  the  once  horizontal  strata.  Suppose  a  force 
of  torsion  to  act  upon  the  promontory  at  its  southern  ex- 
tremity near  Europa  Point,  and  suppose  the  rock  to  be 
of  a  partially  yielding  character  ;  such  a  force  would  twist 
the  strata  into  screw-surfaces,  the  greatest  amount  of 
twisting  being  endured  near  the  point  of  application  of 
the  force.  Such  a  twisting  the  rock  appears  to  have 
suffered ;  but  instead  of  the  twist  fading  gradually  and 
uniformly  off,  in  passing  from  south  to  north,  the  want 
of  uniformity  in  the  material  has  produced  lines  of  dis- 
location where  there  are  abrupt  changes  in  the  amount 
of  twist.  Thus,  at  the  northern  end  of  the  rock  the  dip 
to  the  west  is  nineteen  degrees ;  in  the  Middle  Hill  it  is 
thirty-eight  degrees ;  in  the  centre  of  the  South  Hill,  or 
Sugar  Loaf,  it  is  fifty-seven  degrees.  At  the  southern 
extremity  of  the  Sugar  Loaf  the  strata  are  vertical,  while 


VOYAGE  TO  ALGERIA.  209 

farther  to   the   south  they  actually  turn  over  and   dip  to 
the  east. 

The  rock  is  thus  divided  into  three  sections,  separated 
from  each  other  by  places  of  dislocation,  where  the  strata 
are  much  wrenched  and  broken.  These  are  called  the 
Northern  and  Southern  Quebrada,  from  the  Spanish 
4  Tierra  Quebrada,'  or  broken  ground.  It  is  at  these 
places  that  the  inland  caves  of  Gibraltar  are  almost 
exclusively  found.  Based  on  the  observations  of  Dr. 
Falconer  and  himself,  an  excellent  and  most  interesting 
account  of  these  caves,  and  of  the  human  remains  and  works 
of  art  which  they  contain,  was  communicated  by  Mr.  Busk 
to  the  meeting  of  the  Congress  of  Prehistoric  Archaeology 
at  Norwich,  and  afterwards  printed  in  the  *  Transactions ' 
of  the  Congress.1  Long  subsequently  to  the  operation  of 
the  twisting  force  just  referred  to,  the  promontory  under- 
went various  changes  of  level.  There  are  sea-terraces  and 
layers  of  shell-breccia  along  its  flanks,  and  numerous  caves 
which,  unlike  the  inland  ones,  are  the  product  of  marine 
erosion.  The  Ape's  Hill,  on  the  African  side  of  the  strait, 
Mr.  Busk  informs  me  has  undergone  similar  disturbances.1 

In  the  harbour  of  Gibraltar,  on  the  morning  of  our 
departure,  I  resumed  a  series  of  observations  on  the 
colour  of  the  sea.  On  the  way  out  a  number  of  specimens 
had  been  collected,  with  a  view  to  subsequent  exami- 
nation. But  the  bottles  were  claret  bottles,  of  doubtful 
purity.  At  Gibraltar,  therefore,  I  purchased  fifteen  white 
glass  bottles,  with  ground  glass  stoppers,  and  at  Cadiz, 
thanks  to  the  friendly  guidance  of  Mr.  Cameron,  I  se- 

1  In  this  essay  Mr.  Busk  refers  to  the  previous  labours  of  Mr.  Smith, 
of  Jordan  Hill,  to  whom  we  owe  most  of  our  knowledge  of  the  geology  of 
the  rock. 

2  No  one  can  rise  from  the  perusal  of  Mr.  Busk's  paper  without  a 
feeling  of  admiration  for  the  principal  discoverer  and  indefatigable  ex- 
plorer of  the  Gibraltar  caves,  the  late  Captain  Frederick  Brome. 


210  FRAGMENTS    OF   SCIENCE. 

cured  a  dozen  more.  These  seven-and-twenty  bottlea 
were  filled  with  water,  taken  at  different  places  between 
Oran  and  Spithead.' 

And  here  let  me  express  my  warmest  acknowledgments 
to  Captain  Henderson,  the  commander  of  H.M.S.  '  Urgent,' 
who  aided  me  in  my  observations  in  every  possible  way. 
Indeed,  my  thanks  are  due  to  all  the  officers  for  their 
unfailing  courtesy  and  help.  The  captain  placed  at  my 
disposal  his  own  coxswain,  an  intelligent  fellow  named 
Thorogood,  who  skilfully  attached  a  cord  to  each  bottle, 
weighted  it  with  lead,  cast  it  into  the  sea,  and,  after 
three  successive  rinsings,  filled  it  under  my  own  eyes. 
The  contact  of  jugs,  buckets,  or  other  vessels  was  thus 
avoided  ;  and  even  the  necessity  of  pouring  out  the  water, 
afterwards,  through  the  dirty  London  air. 

The  mode  of  examination  applied  to  these  bottles  has 
been  already  described.1  The  liquid  is  illuminated  by  a 
powerfully  condensed  beam,  its  condition  being  revealed 
through  the  light  scattered  by  its  suspended  particles. 
'  Care  is  taken  to  defend  the  eye  from  the  access  of  all  other 
light,  and,  thus  defended,  it  becomes  an  organ  of  inconceiv- 
able delicacy.'  Were  water  of  uniform  density  perfectly  free 
from  suspended  matter,  it  would,  in  my  opinion,  scatter 
no  light  at  all.  The  track  of  a  luminous  beam  could  not  be 
seen  in  such  water.  But '  an  amount  of  impurity  so  infinite- 
simal as  to  be  scarcely  expressible  in  numbers,  and  the 
individual  particles  of  which  are  so  small  as  wholly  to 
elude  the  microscope,  may,  when  examined  by  the  method 
alluded  to,  produce  not  only  sensible,  but  striking,  effects 
upon  the  eye.' 

The  results  of  the  examination  of  nineteen  bottles 
filled  at  various  places  between  Gibraltar  and  Spithead, 
are  here  tabulated : 

1  On  Dust  and  Disease,  pp.  156,  157. 


VOYAGE   TO   ALGERIA. 


211 


No. 

Locality 

Colour  of  Sea 

Appearance  in  Luminous  Beam 

1 
2 

4 
5 

Gibraltar  Harbour  .    .    . 
Two  mil*-s  from  Gibraltar 
Off  Cabreta  Point  .    .    . 
Off  Cabreta  Point  .    .     . 
Off  Tarif  a  

Green     .    . 

Clearer  green 
Bright  green 
Black-indigo 
Undecided.  . 

Thick  with  fine  particles 
Thick  with  very  fine  particles 
Still  thick,  but  less  so 
Much  less  thick,  very  pure 
Thicker  than  No.  4 

6 
7 

8 
9 
10 
11 

12 
13 
14 
15 
16 
17 

Beyond  Tarifa    .... 
Twelve  miles  from  Cadiz 
Cadiz  Harbour    .... 
Fourteen  miles  from  Cadiz 
Fourteen  mileg  from  Cadiz 
Between  Capes  St.  Mary 
and  Vincent  .... 
Off  the  Burlings  .... 
Beyond  the  Barlings  .     . 
Off  Cape  Finisterre      .     . 
Bay  of  Biscay     .... 
Bay  of  Biscay     .... 
Off  TJshant     . 

Cobalt-blue 
Yellow-green 
Yellow-green 
Yellow-green 
Bright  green 

Deep  indigo 
Strong  green 
Indigo    .    . 
Undecided  . 
Black-indigo 
Indigo    .    . 

Much  purer  than  No.  5 
Very  thick 
Exceedingly  thick 
Thick,  but  less  so 
Much  less  thick 

Very  little  matter,  very  pure 
Thick,  with  fine  matter 
Very  little  matter,  pure 
Less  pure 
Very  little  matter,  very  pure 
Very  fine  matter.    Iridescent 

18 
19 

Off  St.  Catherine's  .    .    . 
Spithead    

Yellow-green 
Green     .    . 

Exceedingly  thick 
Exceedingly  thick 

Here  we  have  three  specimens  of  water,  described  as 
green,  a  clearer  green,  and  bright  green,  taken  in  Gibraltar 
Harbour,  at  a  point  two  miles  from  the  harbour,  and  off 
Cabreta  Point.  The  home  examination  showed  the  first 
to  be  thick  with  suspended  matter,  the  second  less  thick, 
and  the  third  still  less  thick.  Thus  the  green  brightened 
as  the  suspended  matter  diminished  in  amount. 

Previous  to  the  fourth  observation  our  excellent  navi- 
gating lieutenant,  Mr.  Brown,  steered  along  the  coast, 
thus  avoiding  the  adverse  current  which  sets  in,  through 
the  Strait,  from  the  Atlantic  to  the  Mediterranean.  He 
was  at  length  forced  to  cross  the  boundary  of  the  At- 
lantic current,  which  was  defined  with  extraordinary 
sharpness.  On  the  one  side  of  it  the  water  was  a  vivid 
green,  on  the  other  a  deep  blue.  Standing  at  the  bow 
of  the  ship,  a  bottle  could  be  filled  with  blue  water, 
while  at  the  same  moment  a  bottle  cast  from  the  stern 
could  be  filled  with  green  water.  Two  bottles  were  se- 
cured, one  on  each  side  of  this  remarkable  boundary. 
In  the  distance  the  Atlantic  had  the  hue  called  ultra- 
marine ;  but  looked  fairly  down  upon,  it  was  of  almost 
inky  blackness — black  qualified  by  a  trace  of  indigo. 


212  FRAGMENTS   OF   SCIENCE. 

What  change  does  the  home  examination  here  reveal  ? 
In  passing  to  indigo,  the  water  becomes  suddenly  aug- 
mented in  purity,  the  suspended  matter  becoming  sud- 
denly less.  Off  Tarifa,  the  deep  indigo  disappears,  and  the 
sea  is  undecided  in  colour.  Accompanying  this  change, 
we  have  a  rise  in  the  quantity  of  suspended  matter. 
Beyond  Tarifa,  we  change  to  cobalt-blue,  the  suspended 
matter  falling  at  the  same  time  in  quantity.  This  water 
is  distinctly  purer  than  the  green.  We  approach  Cadiz, 
and  at  twelve  miles  from  the  city  get  into  yellow-green 
water  ;  this  the  London  examination  shows  to  be  thick 
with  suspended  matter.  The  same  is  true  of  Cadiz  harbour, 
and  also  of  a  point  fourteen  miles  from  Cadiz  in  the  home- 
ward direction.  Here  there  is  a  sudden  change  from 
yellow-green  to  a  bright  emerald-green,  and  accompanying 
the  change  a  sudden  fall  in  the  quantity  of  suspended 
matter.  Between  Cape  St.  Mary  and  Cape  St.  Vincent 
the  water  changes  to  the  deepest  indigo,  a  further  dimi- 
nution of  the  suspended  matter  being  the  concomitant 
phenomenon. 

We  now  reach  the  remarkable  group  of  rocks  called 
the  Burlings,  and  find  the  water  between  the  shore  and 
the  rocks  a  strong  green  ;  the  home  examination  shows  it 
to  be  thick  with  fine  matter.  Fifteen  or  twenty  miles 
beyond  the  Burlings  we  come  again  into  indigo  water, 
from  which  the  suspended  matter  has  in  great  part  dis- 
appeared. Off  Cape  Finisterre,  about  the  place  where 
the  l  Captain '  went  down,  the  water  becomes  green,  and 
the  home  examination  pronounces  it  to  be  thicker.  Then 
we  enter  the  Bay  of  Biscay,  where  the  indigo  resumes  its 
power,  and  where  the  home  examination  shows  the  greatly 
augmented  purity  of  the  water.  A  second  specimen  of 
water,  taken  from  the  Bay  of  Biscay,  held  in  suspension 
fine  particles  of  a  peculiar  kind ;  the  size  of  them  was 
such  as  to  render  the  water  richly  iridescent.  It  showed 


VOYAGE   TO   ALGERIA.  213 

itself  green,  blue,  or  salmon-coloured,  according  to  the 
direction  of  the  line  of  vision.  Finally,  we  come  to  our 
last  two  bottles,  the  one  taken  opposite  St.  Catherine's 
lighthouse,  in  the  Isle  of  Wight,  the  other  at  Spithead. 
The  sea  at  both  these  places  was  green,  and  both  speci- 
mens, as  might  be  expected,  were  pronounced  by  the  home 
examination  to  be  thick  with  suspended  matter. 

Two  distinct  series  of  observations  are  here  referred  to 
— the  one  consisting  of  direct  observations  of  the  colour 
of  the  sea,  conducted  during  the  voyage  from  Gibraltar  to 
Portsmouth  ;  the  other  carried  out  in  the  laboratory  of  the 
Eoyal  Institution.  And  here  it  is  to  be  noted  that  in  the 
home  examination  I  never  knew  what  water  was  placed  in 
my  hands.  The  labels,  with  the  names  of  the  localities 
written  upon  them,  had  been  tied  up,  all  information 
regarding  the  source  of  the  water  being  thus  held  back. 
The  bottles  were  simply  numbered,  and  not  till  all  of 
them  had  been  examined,  and  described,  were  the  labels 
opened,  and  the  locality  and  sea-colour  corresponding  to  the 
various  specimens  ascertained.  The  home  observations, 
therefore,  must  have  been  perfectly  unbiassed,  and  they 
clearly  establish  the  association  of  the  green  colour  with 
fine  suspended  matter,  and  of  the  ultramarine  colour,  and 
more  especially  of  the  black-indigo  hue  of  the  Atlantic, 
with  the  comparative  absence  of  such  matter. 

So  much  for  mere  observation ;  but  what  is  the  cause  of 
the  dark  hue  of  the  deep  ocean  ? l  A  preliminary  remark 
or  two  will  clear  our  way  towards  an  explanation.  Colour 
resides'in  white  light,  appearing  generally  when  any  consti- 

1  A  note,  written  to  me  on  October  22,  by  my  friend  Canon  Kingsley, 
contains  the  following  reference  to  this  point:  'I  have  never  seen  the 
Lake  of  Geneva,  but  I  thought  of  the  brilliant  dazzling  dark  blue  of  the 
mid-Atlantic  under  the  sunlight,  and  its  black-blue  under  cloud,  both  so 
solid  that  one  might  leap  off  the  sponson  on  to  it  without  fear;  this  was  to 
me  the  most  wonderful  thing  which  I  saw  on  my  voyages  to  and  from  the 
West  Indies." 


214  FRAGMENTS   OP   SCIENCE. 

tuent  of  the  white  light  is  withdrawn.  The  hue  of  a  purple 
liquid,  for  example,  is  immediately  accounted  for  by  its  ac- 
tion on  a  spectrum.  It  cuts  out  the  yellow  and  green,  and 
allows  the  red  and  blue  to  pass  through.  The  blending  of 
these  two  colours  produces  the  purple.  But  while  such  a 
liquid  attacks  with  special  energy  the  yellow  and  green,  it 
enfeebles  the  whole  spectrum.  By  increasing  the  thick- 
ness of  the  stratum  we  may  absorb  the  whole  of  the  light. 
The  colour  of  a  blue  liquid  is  similarly  accounted  for.  It 
first  extinguishes  the  red ;  then,  as  the  thickness  aug- 
ments, it  attacks  the  orange,  yellow,  and  green  in  suc- 
cession ;  the  blue  alone  finally  remaining.  But  even  it 
might  be  extinguished  by  a  sufficient  depth  of  liquid. 

And  now  we  are  prepared  for  a  brief,  but  tolerably 
complete,  statement  of  that  action  of  sea-water  upon 
light,  to  which  it  owes  its  darkness.  The  spectrum  em- 
braces three  classes  of  rays — the  thermal,  the  visual,  and 
the  chemical.  These  divisions  overlap  each  other  ;  the 
thermal  rays  are  in  part  visual,  the  visual  rays  in  part 
chemical,  and  vice  versa.  The  vast  body  of  thermal  rays 
lie  beyond  the  red,  being  invisible.  These  rays  are  attacked 
with  exceeding  energy  by  water.  They  are  absorbed 
close  to  the  surface  of  the  sea,  and  are  the  great  agents  in 
evaporation.  At  the  same  time  the  whole  spectrum  suffers 
enfeeblement ;  water  attacks  all  its  rays,  but  with  different 
degrees  of  energy.  Of  the  visual  rays,  the  red  are  first 
extinguished.  As  the  solar  beam  plunges  deeper  into 
the  sea,  orange  follows  red,  yellow  follows  orange,  green 
follows  yellow,  and  the  various  shades  of  blue,  where  the 
water  is  deep  enough,  follow  green.  Absolute  extinction 
of  the  solar  beam  would  be  the  consequence  if  the  water 
were  deep  and  uniform.  If  it  contained  no  suspended 
matter,  such  water  would  be  as  black  as  ink.  A  re- 
flected glimmer  of  ordinary  light  would  reach  us  from 


VOYAGE   TO   ALGERIA.  215 

its  surface,  as  it  would  from  the  surface  of  actual  ink ; 
but  no  light,  hence  no  colour,  would  reach  us  from  the 
body  of  the  water. 

In  very  clear  and  deep  sea-water  this  condition  is 
approximately  fulfilled,  and  hence  the  extraordinary  dark- 
ness of  such  water.  The  indigo,  already  referred  to, 
is,  I  believe,  to  be  ascribed  in  part  to  the  suspended 
matter,  which  is  never  absent,  even  in  the  purest  natural 
water ;  and  in  part  to  the  slight  reflection  of  the  light 
from  the  limiting  surfaces  of  strata  of  different  densi- 
ties. A  modicum  of  light  is  thus  thrown  back  to  the 
eye,  before  the  depth  necessary  to  absolute  extinction 
has  been  attained.  An  effect  precisely  similar  occurs 
under  the  moraines  of  glaciers.  The  ice  here  is  ex- 
ceptionally compact,  and,  owing  to  the  absence  of  the 
internal  scattering  common  in  bubbled  ice,  the  light 
plunges  into  the  mass,  where  it  is  extinguished,  the  per- 
fectly clear  ice  presenting  an  appearance  of  pitchy  black- 
ness.1 

The  green  colour  of  the  sea  has  now  to  be  accounted 
for  ;  and  here,  again,  let  us  fall  back  upon  the  sure 
basis  of  experiment.  A  strong  white  dinner-plate  had 
a  lead  weight  securely  fastened  to  it.  Fifty  or  sixty  yards 
of  strong  hempen  line  were  attached  to  the  plate.  My 
assistant,  Thorogood,  occupied  a  boat,  fastened  as  usual  to 
the  davits  of  the  '  Urgent,'  while  I  occupied  a  second  boat 
nearer  the  stern  of  the  ship.  He  cast  the  plate  as  a 
mariner  heaves  the  lead,  and  by  the  time  it  had  reached 
me  it  had  sunk  a  considerable  depth  in  the  water.  In 
all  cases  the  hue  of  this  plate  was  green ;  even  when  the 
sea  was  of  the  darkest  indigo,  the  green  was  vivid  and 
pronounced.  I  could  notice  the  gradual  deepening  of  the 

1  I  learn  from  a  correspondent  that  certain  Welsh  tarns,  which  are 
reputed  bottomless,  have  this  inky  hue. 


216  FKAGMENTS    OF   SCIENCE. 

colour  as  the  plate  sank,  but  at  its  greatest  depth,  even  in 
indigo  water,  the  colour  was  still  a  blue-green.1 

Other  observations  confirmed  this  one.  The  '  Urgent ' 
is  a  screw"  steamer,  and  right  over  the  blades  of  the  screw 
was  an  orifice  called  the  screw-well,  through  which  one 
could  look  from  the  poop  down  upon  the  screw.  The 
surface-glimmer,  which  so  pesters  the  eye,  was  here  in  a 
great  measure  removed.  Midway  down,  a  plank  crossed 
the  screw-well  from  side  to  side ;  on  this  I  placed  my- 
self and  observed  the  action  of  the  screw  underneath. 
The  eye  was  rendered  sensitive  by  the  moderation  of  the 
light;  and,  to  remove  still  further  all  disturbing  causes, 
Lieutenant  Walton  had  a  sail  and  tarpaulin  thrown  over 
the  mouth  of  the  well.  Underneath  this  I  perched  my- 
self and  watched  the  screw.  In  an  indigo  sea  the  play  of 
colour  was  indescribably  beautiful,  and  the  contrast  be- 
tween the  water,  which  had  the  screw-blades,  and  that 
which  had  the  bottom  of  the  ocean,  as  a  background,  was 
extraordinary.  The  one  was  of  the  most  brilliant  green, 
the  other  of  the  deepest  ultramarine.  The  surface  of  the 
water  above  the  screw-blade  was  always  ruffled.  Liquid 
lenses  were  thus  formed,  by  which  the  coloured  light 
was  withdrawn  from  some  places  and  concentrated  upon 
others,  the  water  flashing  with  metallic  lustre.  The  screw- 
blades  in  this  case  played  the  part  of  the  dinner-plate  in 
the  former  case,  and  there  were  other  instances  of  a  similar 
kind.  The  white  bellies  of  porpoises  showed  the  green  hue, 
varying  in  intensity  as  the  creatures  swung  to  and  fro  be- 
tween the  surface  and  the  deeper  water.  Foam,  at  a  certain 
depth  below  the  surface,  is  also  green.  In  a  rough  sea  the 
light  which  has  penetrated  the  summit  of  a  wave  sometimes 
reaches  the  eye,  a  beautiful  green  cap  being  thus  placed 
upon  the  wave,  even  in  indigo  water. 

1  In  no  case,  of  course,  is  the  green  pure,  but  a  mixture  of  green  and 
blue. 


VOYAGE   TO  ALGEEIA.  217 

But  how  is  this  colour  to  be  connected  with  the  sus- 
pended particles  ?  Take  the  dinner-plate  which  showed 
so  brilliant  a  green  when  thrown  into  indigo  water. 
Suppose  it  to  diminish  in  size,  until  it  reaches  an  almost 
microscopic  magnitude.  It  would  still  behave  substan- 
tially as  the  larger  plate,  sending  to  the  eye  its  modicum 
of  green  light.  If  the  plate,  instead  of  being  a  large 
coherent  mass,  were  ground  to  a  powder  sufficiently  fine, 
and  in  this  condition  diffused  through  the  clear  sea- 
water,  it  would  send  green  light  to  the  eye.  In  fact,  the 
suspended  particles  which  the  home  examination  reveals, 
act  in  all  essential  particulars  like  the  plate,  or  like  the 
screw-blades,  or  like  the  foam,  or  like  the  bellies  of  the 
porpoises.  Thus  I  think  the  greenness  of  the  sea  is  physi- 
cally connected  with  the  matter  which  it  holds  in  sus- 
pension. 

We  reached  Portsmouth  on  January  5,  1871.  Then 
ended  a  voyage  which,  though  its  main  object  was  not 
realised,  has  left  behind  it  pleasant  memories,  both  of 
the  aspects  of  nature  and  the  kindliness  of  men. 


218  FRAGMENTS   OP   SCIENCE. 


VII. 

NIAGARA. 
1872. 

IT  is  one  of  the  disadvantages  of  reading  books  about 
natural  scenery  that  they  fill  the  mind  with  pictures, 
often  exaggerated,  often  distorted,  often  blurred,  and,  even 
when  well  drawn,  injurious  to  the  freshness  of  first  impres- 
sions. Such  has  been  the  fate  of  most  of  us  with  regard 
to  the  Falls  of  Niagara.  There  was  little  accuracy  in  the 
estimates  of  the  first  observers  of  the  cataract.  Startled 
by  an  exhibition  of  power  so  novel  and  so  grand,  emotion 
leaped  beyond  the  control  of  the  judgment,  and  gave 
currency  to  notions  which  have  often  led  to  disappoint- 
ment. 

A  record  of  a  voyage  in  1535  by  a  French  mariner 
named  Jacques  Cartier,  contains,  it  is  said,  the  first  printed 
allusion  to  Niagara.  In  1603  the  first  map  of  the  district 
was  constructed  by  a  Frenchman  named  Champlain.  In 
1648  the  Jesuit  Eageneau,  in  a  letter  to  his  superior  at 
Paris,  mentions  Niagara  as  'a  cataract  of  frightful  height.' l 
In  the  winter  of  1678  and  1679  the  cataract  was  visited 
by  Father  Hennepin,  and  described  in  a  book  dedicated  'to 
the  King  of  Great  Britain.'  He  gives  a  drawing  of  the 
waterfall,  which  shows  that  serious  changes  have  taken 
place  since  his  time.  He  describes  it  as  '  a  great  and  pro- 

1  From  an  interesting  little  book  presented  to  me  at  Brooklyn  by  its 
author,  Mr.  Holly,  some  of  these  data  are  derived :  Hennepin,  Kalm,  Bake 
•well,  Lyell,  Hall,  and  others  I  have  myself  consulted. 


NIAGARA.  219 

digious  cadence  of  water,  to  which  the  universe  does  not 
offer  a  parallel.'  The  height  of  the  fall,  according  to 
Hennepin,  was  more  than  600  feet.  '  The  waters,'  he  says, 
'  which  fall  from  this  great  precipice  do  foam  and  boil  in 
the  most  astonishing  manner,  making  a  noise  more  terrible 
than  that  of  thunder.  When  the  wind  blows  to  the  south 
its  frightful  roaring  may  be  heard  for  more  than  fifteen 
leagues.'  The  Baron  la  Hontan,  who  visited  Niagara  in 
1687,  makes  the  height  800  feet.  In  1721  Charlevois,  in 
a  letter  to  Madame  de  Maintenon,  after  referring  to  the 
exaggerations  of  his  predecessors,  thus  states  the  result  of 
his  own  observations  :  i  For  my  part,  after  examining  it  on 
all  sides,  I  am  inclined  to  think  that  we  cannot  allow  it 
less  than  140  or  150  feet,' — a  remarkably  close  estimate. 
At  that  time,  viz.  a  hundred  and  fifty  years  ago,  it  had 
the  shape  of  a  horseshoe,  and  reasons  will  subsequently 
be  given  for  holding  that  this  has  been  always  the  form  of 
the  cataract,  from  its  origin  to  its  present  site. 

As  regards  the  noise  of  the  fall,  Charlevois  declares 
the  accounts  of  his  predecessors,  which,  I  may  say,  are 
repeated  to  the  present  hour,  to  be  altogether  extravagant, 
lie  is  perfectly  right.  The  thunders  of  Niagara  are  formi- 
dable enough  to  those  who  really  seek  them  at  the  base  of 
the  Horseshoe  Fall ;  but  on  the  banks  of  the  river,  and 
particularly  above  the  fall,  its  silence,  rather  than  its 
noise,  is  surprising.  This  arises,  in  part,  from  the  lack  of 
resonance ;  the  surrounding  country  being  flat,  and  there- 
fore furnishing  no  echoing  surfaces  to  reinforce  the  shock 
of  the  water.  The  resonance  from  the  surrounding  rocks 
causes  the  Swiss  Eeuss  at  the  Devil's  Bridge,  when  full,  to 
thunder  more  loudly  than  the  Niagara. 

On  Friday,  November  1,  1872,  just  before  reaching 
the  village  of  Niagara  Falls,  I  caught,  from  the  railway 
train,  my  first  glimpse  of  the  smoke  of  the  cataract. 
Immediately  after  my  arrival  I  went  with  a  friend  to 


220  FKAGMSNTS   OF   SCIENCE. 

the  northern  end  of  the  American  Fall.  It  may  be  that 
my  mood  at  the  time  toned  down  the  impression  pro- 
duced by  the  first  aspect  of  this  grand  cascade  ;  but  I 
felt  nothing  like  disappointment,  knowing,  from  old  ex- 
perience, that  time  and  close  acquaintanceship,  the  gradual 
interweaving  of  mind  and  nature,  must  powerfully  influence 
my  final  estimate  of  the  scene.  After  dinner  we  crossed 
to  Goat  Island,  and,  turning  to  the  right,  reached  the 
southern  end  of  the  American  Fall.  The  river  is  here 
studded  with  small  islands.  Crossing  a  wooden  bridge 
to  Luna  Island,  and  clasping  a  tree  which  grows  near  its 
edge,  I  looked  long  at  the  cataract,  which  here  shoots 
down  the  precipice  like  an  avalanche  of  foam.  It  grew 
in  power  and  beauty.  The  channel  spanned  by  the 
wooden  bridge  was  deep,  and  the  river  there  doubled 
over  the  edge  of  the  precipice,  like  the  swell  of  a  muscle, 
unbroken.  The  ledge  here  overhangs,  the  water  being 
poured  out  far  beyond  the  base  of  the  precipice.  A  space, 
called  the  Cave  of  the  Winds,  is  thus  enclosed  between 
the  wall  of  rock  and  the  falling  water. 

Goat  Island  ends  in  a  sheer  dry  precipice,  which 
connects  the  American  and  Horseshoe  Falls.  Midway 
between  both  is  a  wooden  hut,  the  residence  of  the  guide 
to  the  Cave  of  the  Winds,  and  from  the  hut  a  winding 
staircase,  called  Biddle's  Stair,  descends  to  the  base  of 
the  precipice.  On  the  evening  of  my  arrival  I  went  down 
this  stair,  and  wandered  along  the  bottom  of  the  cliff. 
One  well-known  factor  in  the  formation  and  retreat  of  the 
cataract  was  immediately  observed.  A  thick  layer  of 
limestone  formed  the  upper  portion  of  the  cliff.  This 
rested  upon  a  bed  of  soft  shale,  which  extended  round  the 
base  of  the  cataract.  The  violent  recoil  of  the  watei 
against  this  yielding  substance  crumbles  it  away,  under- 
mining the  ledge  above,  which,  unsupported,  eventually 
breaks  off,  and  produces  the  observed  recession. 


NIAGARA.  221 

At  the  southern  jxtremity  of  the  Horseshoe  is  a  pro- 
montory, formed  by  the  doubling  back  of  the  gorge,  ex- 
cavated by  the  cataract,  and  into  which  it  plunges.  On 
the  promontory  stands  a  stone  building,  called  the  Terrapin 
Tower,  the  door  of  which  had  been  nailed  up  because  of 
the  decay  of  the  staircase  within  it.  Through  the  kind- 
ness of  Mr.  Townsend,  the  superintendent  of  Groat  Island, 
the  door  was  opened  for  me.  From  this  tower,  at  all 
hours  of  the  day,  and  at  some  hours  of  the  night,  I  watched 
and  listened  to  the  Horseshoe  Fall.  The  river  here  if, 
evidently  much  deeper  than  the  American  branch ;  and 
instead  of  bursting  into  foam  where  it  quits  the  ledge, 
it  bends  solidly  over,  and  falls  in  a  continuous  layer 
of  the  most  vivid  green.  The  tint  is  not  uniform ; 
long  stripes  of  deeper  hue  alternating  with  bands  of 
brighter  colour.  Close  to  the  ledge  over  which  the  water 
rolls,  foam  is  generated,  the  light  falling  upon  which,  and 
flashing  back  from  it,  is  sifted  in  its  passage  to  and  fro, 
and  changed  from  white  to  emerald-green.  Heaps  of 
superficial  foam  are  also  formed  at  intervals  along  the 
ledge,  and  are  immediately  drawn  into  long  white  striaB.1 
Lower  down,  the  surface,  shaken  by  the  reaction  from 
below,  incessantly  rustles  into  whiteness.  The  descent 
finally  resolves  itself  into  a  rhythm,  the  water  reaching  the 
bottom  of  the  fall  in  periodic  gushes.  Nor  is  the  spray 
uniformly  diffused  through  the  air,  but  is  wafted  through 
t  in  successive  veils  of  gauze-like  texture.  From  all  this 
it  is  evident  that  beauty  is  not  absent  from  the  Horseshoe 
Fall,  but  majesty  is  its  chief  attribute.  The  plunge  of 
the  water  is  not  wild,  but  deliberate,  vast,  and  fascinating. 
From  the  Terrapin  Tower,  the  adjacent  arm  of  the  Horse- 
shoe is  seen  projected  against  the  opposite. one,  midway 


1  The  direction  of  the  wind  with  reference  to  the  course  of  a  ship  may 
be  inferred  with  accuracy  from  the  foam-streaks  on  the  surface  of  the  sea. 


222  FRAGMENTS    OF   SCIENCE. 

down ;  to  the  imagination,  therefore,  is  left  the  picturing 
of  the  gulf  into  which  the  cataract  plunges. 

The  delight  which  natural  scenery  produces  in  some 
minds  is  difficult  to  explain,  and  the  conduct  which  it 
prompts  can  hardly  be  fairly  criticised  by  those  who  have 
never  experienced  it.  It  seems  to  me  a  deduction  from 
the  completeness  of  the  celebrated  Thomas  Young,  that 
he  was  unable  to  appreciate  natural  scenery.  '  He  had 
really,'  says  Dean  Peacock,  *  no  taste  for  life  in  the 
country ;  he  was  one  of  those  who  thought  that  no  one 
who  was  able  to  live  in  London  would  be  content  to  live 
elsewhere.'  Well,  Dr.  Young,  like  Dr.  Johnson,  had  a 
right  to  his  delights ;  but  I  can  understand  a  hesitation 
to  accept  them,  high  as  they  were,  to  the  exclusion  of 

That  o'erflowing  joy  which  Nature  yields 
To  her  true  lovers. 

To  all  who  are  of  this  mind,  the  strengthening  of  desire 
on  my  part  to  see  and  know  Niagara  Falls,  as  far  as  it 
is  possible  for  them  to  be  seen  and  known,  will  be  intel- 
ligible. 

On  the  first  evening  of  my  visit,  I  met,  at  the  head  of 
Biddle's  Stair,  the  gmde  to  the  Cave  of  the  Winds.  He 
was  in  the  prime  of  manhood — large,  well  built,  firm  and 
pleasant  in  mouth  and  eye.  My  interest  in  the  scene 
stirred  up  his,  and  made  him  communicative.  Turning 
to  a  photograph,  he  described,  by  reference  to  it,  a  feat 
which  he  had  accomplished  some  time  previously,  and 
which  had  brought  him  almost  under  the  green  water  of 
the  Horseshoe  Fall.  '  Can  you  lead  me  there  to-morrow  ?' 
I  asked.  He  eyed  me  enquiringly,  weighing,  perhaps,  the 
chances  of  a  man  of  light  build,  and  with  grey  in  his 
whiskers,  in  such  an  undertaking.  '  I  wish,'  I  added,  '  to 
see  as  much  of  the  fall  as  can  be  seen,  and  where  you  lead 
I  will  endeavour  to  follow.'  His  scrutiny  relaxed  into  a 


NJAGAEA.  223 

smile,  and  he  said,  *  Very  well ;  I  shall  be  ready  for  you 
to-morrow.' 

On  the  morrow,  accordingly,  I  came.  In  the  hut  at 
the  head  of  Biddle's  Stair  I  stripped  wholly,  and  re- 
dressed according  to  instructions, — drawing  on  two  pairs  of 
woollen  pantaloons,  three  woollen  jackets,  two  pairs  of 
socks,  and  a  pair  of  felt  shoes.  Even  if  wet,  my  guide 
assured  me  that  the  clothes  would  keep  me  from  being 
chilled ;  and  he  was  right.  A  suit  and  hood  of  yellow  oilcloth 
covered  all.  Most  laudable  precautions  were  taken  by 
the  young  assistant  who  helped  to  dress  me  to  keep  the 
water  out ;  but  his  devices  broke  down  immediately  when 
severely  tested. 

We  descended  the  stair;  the  handle  of  a  pitchfork 
doing,  in  my  case,  the  duty  of  an  alpenstock.  At  the 
bottom,  the  guide  enquired  whether  we  should  go  first  to 
the  Cave  of  the  Winds,  or  to  the  Horseshoe,  remarking 
that  the  latter  would  try  us  most.  I  decided  on  getting 
the  roughest  done  first,  and  he  turned  to  the  left  over  the 
stones.  They  were  sharp  and  trying.  The  base  of  the 
first  portion  of  the  cataract  is  covered  with  huge  boulders, 
obviously  the  ruins  of  the  limestone  ledge  above.  The 
water  does  not  distribute  itself  uniformly  among  these,  but 
seeks  for  itself  channels  through  which  it  pours  torrentially. 
We  passed  some  of  these  with  wetted  feet,  but  without  diffi- 
culty. At  length  we  came  to  the  side  of  a  more  formidable 
current.  My  guide  walked  along  its  edge  until  he  reached 
its  least  turbulent  portion.  Halting,  he  said,  *  This  is 
our  greatest  difficulty  ;  if  we  can  cross  here,  we  shall  get 
far  towards  the  Horseshoe.' 

He  waded  in.  It  evidently  required  all  his  strength 
to  steady  him.  The  water  rose  above  his  loins,  and  it 
foamed  still  higher.  He  had  to  search  for  footing,  amid 
unseen  boulders,  against  which  the  torrent  rose  violently. 
He  struggled  and  swayed,  but  he  struggled  successfully, 


224  FRAGMENTS    OF   SCIENCE. 

and  finally  reached  the  shallower  water  at  the  other  side. 
Stretching  out  his  arm,  he  said  to  me,  '  Now  come  on.'  I 
looked  down  the  torrent,  as  it  rushed  to  the  river  below, 
which  was  seething  with  the  tumult  of  the  cataract.  De 
Saussure  recommended  the  inspection  of  Alpine  dangers, 
with  the  view  of  making  them  familiar  to  the  eye  before 
they  are  encountered ;  and  it  is  a  wholesome  custom  in 
places  of  difficulty  to  put  the  possibility  of  an  accident 
clearly  before  the  mind,  and  to  decide  beforehand  what 
ought  to  be  done  should  the  accident  occur.  Thus  wound 
up  in  the  present  instance,  I  entered  the  water.  Even 
where  it  was  not  more  than  knee-deep,  its  power  was 
manifest.  As  it  rose  around  me,  I  sought  to  split  the 
torrent  by  presenting  a  side  to  it ;  but  the  insecurity  of 
the  footing  enabled  it  to  grasp  my  loins,  twist  me  fairly 
round,  and  bring  its  impetus  to  bear  upon  my  back. 
Further  struggle  was  impossible  ;  and  feeling  my  balance 
hopelessly  gone,  I  turned,  flung  myself  towards  the  bank 
just  quitted,  and  was  instantly,  as  expected,  swept  into 
shallower  water. 

The  oilcloth  covering  was  a  great  iucumbrance ;  it 
had  been  made  for  a  much  stouter  man,  and,  standing  up- 
right after  my  submersion,  my  legs  occupied  the  centre 
of  two  bags  of  water.  My  guide  exhorted  me  to  try 
again.  Prudence  was  at  my  elbow,  whispering  dissuasion ; 
but,  taking  everything  into  account,  it  appeared  more  im- 
moral to  retreat  than  to  proceed.  Instructed  by  the  first 
misadventure,  I  once  more  entered  the  stream.  Had  the 
alpenstock  been  of  iron  it  might  have  helped  me ;  but,  as 
it  was,  the  tendency  of  the  water  to  sweep  it  out  of  my 
hands  rendered  it  worse  than  useless.  I,  however,  clung 
to  it  by  habit.  Again  the  torrent  rose,  and  again  I 
wavered ;  but,  by  keeping  the  left  hip  well  against  it,  I 
remained  upright,  and  at  length  grasped  the  hand  of  my 
leader  at  the  other  side.  He  laughed  pleasantly.  The 


NIAGARA.  228 

first  victory  was  gained,  and  he  enjoyed  it.  'No  traveller,' 
he  said,  '  was  ever  here  before.'  Soon  afterwards,  by 
trusting  to  a  piece  of  drift-wood  which  seemed  firm,  I 
was  again  taken  off  my  feet,  but  was  immediately  caught 
by  a  protruding  rock. 

We  clambered  over  the  boulders  towards  the  thickest 
spray,  which  soon  became  so  weighty  as  to  cause  us  to 
stagger  under  its  shock.  For  the  most  part  nothing  could 
be  seen ;  we  were  in  the  midst  of  bewildering  tumult, 
lashed  by  the  water,  which  sounded  at  times  like  the 
cracking  of  innumerable  whips.  Underneath  this  was 
the  deep  resonant  roar  of  the  cataract.  I  tried  to  shield 
my  eyes  with  my  hands,  and  look  upwards ;  but  the  de- 
fence was  useless.  The  guide  continued  to  move  on,  but 
at  a  certain  place  he  halted,  and  desired  me  to  take  shelter 
in  his  lee,  and  observe  the  cataract.  The  spray  did  not 
come  so  much  from  the  tipper  ledge,  as  from  the  rebound 
of  the  shattered  water  when  it  struck  the  bottom.  Hence 
the  eyes  could  be  protected  from  the  blinding  shock  of 
the  spray,  while  the  line  of  vision  to  the  upper  ledges  re- 
mained to  some  extent  clear.  On  looking  upwards  over 
the  guide's  shoulder  I  could  see  the  water  bending  over 
the  ledge,  while  the  Terrapin  Tower  loomed  fitfully 
through  the  intermittent  spray-gusts.  We  were  right 
under  the  tower.  A  little  farther  on  the  cataract,  after 
its  first  plunge,  hit  a  protuberance  some  way  down,  and 
flew  from  it  in  a  prodigious  burst  of  spray ;  through  this 
we  staggered.  We  rounded  the  promontory  on  which  the 
Terrapin  Tower  stands,  and  moved,  amid  the  wildest 
commotion,  along  the  arm  of  the  Horseshoe,  until  the 
boulders  failed  us,  and  the  cataract  fell  into  the  profound 
gorge  of  the  Niagara  River. 

Here  the  guide  sheltered  me  again,  and  desired  me  to 
look  up ;  I  did  so,  and  could  see,  as  before,  the  green 
gleam  of  the  mighty  curve  sweeping  over  the  upper  ledge, 


228  FRAGMENTS   OF   SCIENCE. 

and  the  fitful  plunge  of  the  water,  as  the  spray  between  ua 
and  it  alternately  gathered  and  disappeared.  An  emi- 
nent friend  of  mine  often  speaks  of  the  mistake  of  those 
physicians  who  regard  man's  ailments  as  purely  chemical, 
to  be  met  by  chemical  remedies  only.  He  contends  for 
the  psychological  element  of  cure.  By  agreeable  emotions, 
he  says,  nervous  currents  are  liberated  which  stimulate 
blood,  brain,  and  viscera.  The  influence  rained  from 
ladies'  eyes  enables  my  friend  to  thrive  on  dishes  which 
would  kill  him  if  eaten  alone.  A  sanative  effect  of  the 
same  order  I  experienced  amid  the  spray  and  thunder  of 
Niagara.  Quickened  by  the  emotions  there  aroused,  the 
blood  sped  exultingly  through  the  arteries,  abolishing 
introspection,  clearing  the  heart  of  all  bitterness,  and 
enabling  one  to  think  with  tolerance,  if  not  with  tender- 
ness, on  the  most  relentless  and  unreasonable  foe.  Apart 
from  its  scientific  value,  and  purely  as  a  moral  agent,  the 
play  was  worth  the  candle.  My  companion  knew  no 
more  of  me  than  that  I  enjoyed  the  wildness  ;  but  as  I 
bent  in  the  shelter  of  his  large  frame  he  said,  '  I  should 
like  to  see  you  attempting  to  describe  all  this.'  He 
rightly  thought  it  indescribable.  The  name  of  this  gallant 
fellow  was  Thomas  Conroy. 

We  returned,  clambering  at  intervals  up  and  down,  so 
as  to  catch  glimpses  of  the  most  impressive  portions  of 
the  cataract.  We  passed  under  ledges  formed  by  tabular 
masses  of  limestone,  and  through  some  curious  openings 
formed  by  the  falling  together  of  the  summits  of  the 
rocks.  At  length  we  found  ourselves  beside  our  enemy 
of  the  morning.  Conroy  halted  for  a  minute  or  two, 
scanning  the  torrent  thoughtfully.  I  said  that,  as  a 
guide,  he  ought  to  have  a  rope  in  such  a  place ;  but  he 
retorted  that,  as  no  traveller  had  ever  thought  of  coming 
there,  he  did  not  see  the  necessity  of  keeping  a  rope.  He 
waded  in.  The  struggle  to  keep  himself  erect  was  evident 


NIAGARA.  227 

enough  ;  he  swayed,  hut  recovered  himself  again  and 
again.  At  length  hs  slipped,  gave  way,  did  as  I  had 
done,  threw  himself  towards  the  bank,  and  was  swept  into 
the  shallows.  Standing  in  the  stream  near  its  edge,  he 
stretched  his  arm  towards  me.  I  retained  the  pitchfork- 
handle,  for  it  had  been  useful  among  the  boulders.  By 
wading  some  way  in,  the  staff  could  be  made  to  reach  him, 
and  I  proposed  his  seizing  it.  '  If  you  are  sure,'  he  replied, 
*  that,  in  case  of  giving  way,  you  can  maintain  your  grasp, 
then  I  will  certainly  hold  you.'  Eemarking  that  he  might 
count  on  this,  I  waded  in,  and  stretched  the  staff  to  my  com- 
panion. It  was  firmly  grasped  by  both  of  us.  Thus  helped, 
though  its  onset  was  strong,  I  moved  safely  across  the  tor- 
rent. All  danger  ended  here.  We  afterwards  roamed  soci- 
ably among  the  torrents  and  boulders  below  the  Cave  of  the 
Winds.  The  rocks  were  covered  with  organic  slime,  which 
could  not  have  been  walked  over  with  bare  feet,  but  the 
felt  shoes  effectually  prevented  slipping.  We  reached  the 
cave  and  entered  it,  first  by  a  wooden  way  carried  over  the 
boulders,  and  then  along  a  narrow  ledge,  to  the  point  eaten 
deepest  into  the  shale.  When  the  wind  is  from  the  south, 
the  falling  water,  I  am  told,  can  be  seen  tranquilly  from 
this  spot ;  but  when  we  were  there,  a  blinding  hurricane 
of  spray  was  whirled  against  us.  On  the  evening  of  the 
same  day,  I  went  behind  the  water  on  the  Canada  side, 
which,  after  the  experiences  of  the  morning,  struck  me 
as  an  imposture. 

Still  even  this  latter  is  exciting  to  some  nerves.  Its 
effects  upon  himself  is  thus  vividly  described  by  Mr. 
Bakewell,  jun. :  '  On  turning  a  sharp  angle  of  the  rock,  a 
sudden  gust  of  wind  met  us,  coming  from  the  hollow 
between  the  fall  and  the  rock,  which  drove  the  spray 
directly  in  our  faces,  with  such  force  that  in  an  instant 
we  were  wet  through.  When  in  the  midst  of  this  shower- 
bath  the  shock  took  away  my  breath  :  I  turned  back  and 


228  FEAGMENTS   OF   SCIENCE. 

scrambled  over  the  loose  stones  to  escape  the  conflict. 
The  guide  soon  followed,  and  told  me  that  I  had  passed 
the  worst  part.  With  that  assurance  I  made  a  second 
attempt ;  but  so  wild  and  disordered  was  my  imagination 
that  when  I  had  reached  half  way  I  could  bear  it  no 
longer.'  * 

To  complete  my  knowledge  I  desired  to  see  the  fall 
from  the  river  below  it,  and  long  negotiations  were  ne- 
cessary to  secure  the  means  of  doing  so.  The  only  boat 
fit  for  the  undertaking  had  been  laid  up  for  the  winter; 
but  this  difficulty,  through  the  kind  intervention  of  Mr. 
Townsend,  was  overcome.  The  main  one  was  to  secure 
oarsmen  sufficiently  strong  and  skilful  to  urge  the  boat 
where  I  wished  it  to  be  taken.  The  son  of  the  owner  of 
the  boat,  a  finely-built  young  fellow,  but  only  twenty,  and 
therefore  not  sufficiently  hardened,  was  willing  to  go ;  and 
up  the  river,  it  was  stated,  there  lived  another  man  who 
would  do  anything  with  the  boat  which  strength  and 
daring  could  accomplish.  He  came.  His  figure  and 
expression  of  face  certainly  indicated  extraordinary  firm- 
ness and  power.  On  Tuesday,  November  5,  we  started, 
each  of  us  being  clad  in  oilcloth.  The  elder  oarsman 
at  once  assumed  a  tone  of  authority  over  his  companion, 
and  struck  immediately  in  amid  the  breakers  below  the 
American  Fall.  He  hugged  the  cross  freshets  instead 
of  striking  out  into  the  smoother  water.  I  asked  him 
why  he  did  so,  and  he  replied  that  they  were  directed 
outivards,  not  downwards.  The  struggle,  however,  to 
prevent  the  bow  of  the  boat  from  being  turned  by  them, 
was  often  very  severe. 

The  spray  was  in  general  blinding,  but  at  times  it 
disappeared  and  yielded  noble  views  of  the  fall.  The 
edge  of  the  cataract  is  crimped  by  indentations  which 

1  'Mag.  of  Nat  Hist.,'  1830,  pp.  121,  122. 


NIAGARA.  229 

exalt  its  beauty.  Here  and  there,  a  little  below  the 
highest  ledge,  a  secondary  one  juts  out ;  the  water  strikes 
it  and  bursts  from  it  in  huge  protuberant  masses  of  foam 
and  spray.  We  passed  Goat  Island,  came  to  the  Horse- 
shoe, and  worked  for  a  time  along  the  base  of  it,  the 
boulders  over  which  Conroy  and  myself  had  scrambled  a 
few  days  previously  lying  between  us  and  the  base.  A 
rock  was  before  us,  concealed  and  revealed  at  intervals,  as 
the  waves  passed  over  it.  Our  leader  tried  to  get  above 
this  rock,  first  on  the  outside  of  it.  The  water,  however, 
was  here  in  violent  motion.  The  men  struggled  fiercely, 
the  older  one  ringing  out  an  incessant  peal  of  command 
and  exhortation  to  the  younger.  As  we  were  just  clearing 
the  rock,  the  bow  came  obliquely  to  the  surge ;  the  boat 
was  turned  suddenly  round  and  shot  with  astonishing 
rapidity  down  the  river.  The  men  returned  to  the  charge, 
now  trying  to  get  up  between  the  half-concealed  rock  and 
the  boulders  to  the  left.  But  the  torrent  set  in  strongly 
through  this  channel.  The  tugging  was  quick  and  violent, 
but  we  made  little  way.  At  length,  seizing  a  rope,  the 
principal  oarsman  made  a  desperate  attempt  to  get  upon 
one  of  the  boulders,  hoping  to  be  able  to  drag  the  boat 
through  the  channel;  but  it  bumped  so  violently  against 
the  rock,  that  the  man  flung  himself  back  and  relinquished 
the  attempt. 

"We  returned  along  the  base  of  the  American  Fall, 
running  in  and  out  among  the  currents  which  rushed 
from  it  laterally  into  the  river.  Seen  from  below  the 
American  Fall  is  certainly  exquisitely  beautiful,  but  it  is 
a  mere  frill  of  adornment  to  its  nobler  neighbour  the 
Horseshoe.  At  times  we  took  to  the  river,  from  the 
centre  of  which  the  Horseshoe  Fall  appeared  especially 
magnificent.  A  streak  of  cloud  across  the  neck  of  Mont 
Blanc  can  double  its  apparent  height,  so  here  the  green 
summit  of  the  cataract  shining  above  the  smoke  of  spray 


230  FRAGMENTS    OF   SCIENCE. 

appeared  lifted  to  an  extraordinary  elevation.  Had 
Hennepin  and  La  Hontan  seen  the  fall  from  this  position, 
their  estimates  of  the  height  would  have  been  perfectly 
excusable. 

From  a  point  a  little  way  below  the  American  Fall,  a 
ferry  crosses  the  river,  in  summer,  to  the  Canadian  side. 
Below  the  ferry  is  a  suspension  bridge  for  carriages  and 
foot-passengers,  and  a  mile  or  two  lower  down  is  the 
railway  suspension  bridge.  Between  the  ferry  and  the 
latter  the  river  Niagara  flows  unruffled ;  but  at  the  sus- 
pension bridge  the  bed  steepens  and  the  river  quickens  its 
motion.  Lower  down  the  gorge  narrows,  and  the  rapidity  and 
turbulence  increase.  At  the  place  called  the  '  Whirlpool 
Rapids '  I  estimated  the  width  of  the  river  at  300  feet,  an 
estimate  confirmed  by  the  dwellers  on  the  spot.  When  it 
is  remembered  that  the  drainage  of  nearly  half  a  continent 
is  compressed  into  this  space,  the  impetuosity  of  the 
river's  escape  through  this  gorge  may  be  imagined.  Had 
it  not  been  for  Mr.  Bierstadt,  the  distinguished  photo- 
grapher of  Niagara,  I  should  have  quitted  the  place 
without  seeing  these  rapids  ;  for  this,  and  for  his  agreeable 
company  to  the  spot,  I  have  to  thank  him.  From  the 
edge  of  the  cliff  above  the  rapids,  we  descended,  a  little  I 
confess  to  a  climber's  disgust,  in  an '  elevator,'  because  the 
effects  are  best  seen  from  the  water  level. 

Two  kinds  of  motion  are  here  obviously  active,  a 
motion  of  translation  and  a  motion  of  undulation — the 
race  of  the  river  through  its  gorge,  and  the  great  waves 
generated  by  its  collision  with,  and  rebound  from,  the 
obstacles  in  its  way.  In  the  middle  of  the  river  the  rush 
and  tossing  are  most  violent ;  at  all  events,  the  impetuous 
force  of  the  individual  waves  is  here  most  strikingly  dis- 
played. Vast  pyramidal  heaps  leap  incessantly  from  the 
river,  some  of  them  with  such  energy  as  to  jerk  their  sum- 


NIAGARA.  231 

mits  into  the  air,  where  they  hang  suspended  as  bundles  of 
liquid  spherules.  The  sun  shone  for  a  few  minutes.  At 
times  the  wind,  coming  up  the  river,  searched  and  sifted 
the  spray,  carrying  away  the  lighter  drops,  and  leaving  the 
heavier  ones  behind.  Wafted  in  the  proper  direction, 
rainbows  appeared  and  disappeared  fitfully  in  the  lighter 
mist.  In  other  directions  the  common  gleam  of  the  sun- 
shine from  the  waves  and  their  shattered  crests  was  exqui- 
sitely beautiful.  The  complexity  of  the  action  was  still 
further  illustrated  by  the  fact,  that  in  some  cases,  as  if  by 
the  exercise  of  a  local  explosive  force,  the  drops  were  shot 
radially  from  a  particular  centre,  forming  around  it  a  kind 
of  halo. 

The  first  impression,  and,  indeed,  the  current  explana- 
tion of  these  rapids  is,  that  the  central  bed  of  the  river  is 
cumbered  with  large  boulders,  and  that  the  jostling, 
tossing,  and  wild  leaping  of  the  water  there,  are  due  to  its 
impact  against  these  obstacles.  I  doubt  this  explanation. 
At  all  events,  there  is  another  sufficient  reason  to  be  taken 
into  account.  Boulders  derived  from  the  adjacent  cliffs 
visibly  cumber  the  sides  of  the  river.  Against  these  the 
water  rises  and  sinks  rhythmically  but  violently,  large 
waves  being  thus  produced.  On  the  generation  of  each 
wave,  there  is  an  immediate  compounding  of  the  wave- 
motion  with  the  river-motion.  The  ridges,  which  in  still 
water  would  proceed  in  circular  curves  round  the  centre  of 
disturbance,  cross  the  river  obliquely,  and  the  result  is 
that  at  the  centre  waves  commingle,  which  have  really  been 
generated  at  the  sides.  In  the  first  instance,  we  had  a 
composition  of  wave-motion  with  river-motion;  here  we 
have  the  coalescence  of  waves  with  waves.  Where  crest 
and  furrow  cross  each  other,  the  motion  is  annulled ;  where 
furrow  and  furrow  cross,  the  river  is  ploughed  to  a  greater 
depth ;  and  where  crest  and  crest  aid  each  other,  we  have 
that  astonishing  leap  of  the  water  which  breaks  the  cohe- 


232  FRAGMENTS   OF   SCIENCE. 

pion  of  the  crests,  and  tosses  them  shattered  into  the  air. 
From  the  water  level  the  cause  of  the  action  is  not  so 
easily  seen ;  but  from  the  summit  of  the  cliff  the  lateral 
generation  of  the  waves,  and  their  propagation  to  the 
centre,  are  perfectly  obvious.  If  this  explanation  be  cor- 
rect, the  phenomena  observed  at  the  Whirlpool  Eapida 
form  one  of  the  grandest  illustrations  of  the  principle  of 
interference.  The  Nile  '  cataract,'  Mr  Huxley  informs  me, 
offers  more  moderate  examples  of  the  same  action. 

At  some  distance  below  the  Whirlpool  Eapids  we  have 
the  celebrated  whirlpool  itself.  Here  the  river  makes  a 
sudden  bend  to  the  north-east,  forming  nearly  a  right  angle 
with  its  previous  direction.  The  water  strikes  the  con- 
cave bank  with  great  force,  and  scoops  it  incessantly  away. 
A  vast  basin  has  been  thus  formed,  in  which  the  sweep 
of  the  river  prolongs  itself  in  gyratory  currents.  Bodies 
and  trees  which  have  come  over  the  falls,  are  stated  to  cir- 
culate here  for  days  without  finding  the  outlet.  From 
various  points  of  the  cliffs  above,  this  is  curiously  hidden. 
The  rush  of  the  river  into  the  whirlpool  is  obvious  enough  ; 
and  though  you  imagine  the  outlet  must  be  visible,  if  one 
existed,  you  cannot  find  it.  Turning,  however,  round  the 
bend  of  the  precipice  to  the  north-east,  the  outlet  comes 
into  view. 

The  Niagara  season  was  over ;  the  chatter  of  sight- 
seers had  ceased,  and  the  scene  presented  itself  as  one  of 
holy  seclusion  and  beauty.  I  went  down  to  the  river's 
edge,  where  the  weird  loneliness  seemed  to  increase.  The 
basin  is  enclosed,  by  high  and  almost  precipitous  bunks 
— covered,  at  the  time,  with  russet  woods.  A  kind  of 
mystery  attaches  itself  to  gyrating  water,  due  perhaps  to 
the  fact  that  we  are  to  some  extent  ignorant  of  the  direc- 
tion of  its  force.  It  is  said  that  at  certain  points  of  the 
whirlpool  pine-trees  are  sucked  down,  to  be  ejected  mys- 
teriously elsewhere.  The  water  is  of  the  brightest  emerald- 


NIAGARA.  233 

green.  The  gorge  through  which  it  escapes  is  narrow, 
and  the  motion  of  the  river  swift  though  silent.  The 
surface  is  steeply  inclined,  but  it  is  perfectly  unbroken. 
There  are  no  lateral  waves,  no  ripples  with  their  breaking 
bubbles  to  raise  a  murmur ;  while  the  depth  is  here  too 
great  to  allow  the  inequality  of  the  bed  to  ruffle  the  sur- 
face. Nothing  can  be  more  beautiful  than  this  sloping 
liquid  mirror  formed  by  the  Niagara,  in  sliding  from  the 
whirlpool. 

The  green  colour  is,  I  think,  correctly  accounted 
for  in  Fragment  VI.  In  crossing  the  Atlantic  I  had 
frequent  opportunities  of  testing  the  explanation  there 
given.  Looked  properly  down  upon,  there  are  portions 
of  the  ocean  to  which  we  should  hardly  ascribe  a  trace 
of  blue ;  at  the  most,  a  hint  of  indigo  reaches  the  eye. 
The  water,  indeed,  is  practically  black,  and  this  is  an 
indication  both  of  its  depth  and  its  freedom  from  mechani- 
cally suspended  matter.  In  small  thicknesses  water  i  •. 
sensibly  transparent  to  all  kinds  of  light ;  but,  as  the 
thickness  increases,  the  rays  of  low  refrangibility  are  first 
absorbed,  and  after  them  the  other  rays.  Where,  there- 
fore, the  water  is  very  deep  and  very  pure,  all  the  colours 
are  absorbed,  and  such  water  ought  to  appear  black,  as  no 
light  is  sent  from  its  interior  to  the  eye.  The  approxima- 
tion of  the  Atlantic  Ocean  to  this  condition  is  an  indica- 
tion of  its  extreme  purity. 

Throw  a  white  pebble  into  such  water  ;  as  it  sinks  it 
becomes  greener  and  greener,  and,  before  it  disappears,  it 
reaches  a  vivid  blue-green.  Break  such  a  pebble  into 
fragments,  each  of  these  will  behave  like  the  unbroken 
mass ;  grind  the  pebble  to  powder,  every  particle  will  yield 
its  modicum  of  green  ;  and  if  the  particles  be  so  fine  as  to 
remain  suspended  in  the  water,  the  scattered  light  will  be 
a  uniform  green.  Hence  the  greenness  of  shoal  water. 
You  go  to  bed  with  the  black  Atlantic  around  you. 


234  FRAGMENTS   OF   SCIENCE. 

You  rise  in  the  morning,  find  it  a  vivid  green,  and 
correctly  infer  that  you  are  crossing  the  bank  of  New- 
foundland. Such  water  is  found  charged  with  fine 
matter  in  a  state  of  mechanical  suspension.  The  light 
from  the  bottom  may  sometimes  corne  into  play,  but 
it  is  not  necessary.  A  storm  can  render  the  water  muddy, 
by  rendering  the  particles  too  numerous  and  gross.  Such 
a  case  occurred  towards  the  close  of  my  visit  to  Niagara. 
There  had  been  rain  and  storm  in  the  upper-lake  regions, 
and  the  quantity  of  suspended  matter  brought  down  quite 
extinguished  the  fascinating  green  of  the  Horseshoe. 

Nothing  can  be  more  superb  than  the  green  of  the 
Atlantic  waves,  when  the  circumstances  are  favourable  to 
the  exhibition  of  the  colour.  As  long  as  a  wave  remains 
unbroken  no  colour  appears ;  but  when  the  foam  just 
doubles  over  the  crest,  like  an  Alpine  snow-cornice,  under 
the  cornice  we  often  see  a  display  of  the  most  exquisite 
green.  It  is  metallic  in  its  brilliancy.  But  the  foam  is 
necessary  to  its  production.  The  foam  is  first  illuminated, 
and  it  scatters  the  light  in  all  directions ;  the  light  which 
passes  through  the  higher  portion  of  the  wave  alone 
reaches  the  eye,  and  gives  to  that  portion  its  matchless 
colour.  The  folding  of  the  wave,  producing,  as  it  does, 
a  series  of  longitudinal  protuberances  and  furrows  which 
act  like  cylindrical  lenses,  introduces  variations  in  the 
intensity  of  the  light,  and  materially  enhances  its  beauty. 

We  have  now  to  consider  the  genesis  and  proximate 
destiny  of  the  Falls  of  Niagara.  We  may  open  our 
way  to  this  subject  by  a  few  preliminary  remarks  upon 
erosion.  Time  and  intensity  are  the  main  factors  of 
geologic  change,  and  they  are  in  a  certain  sense  con- 
vertible. A  feeble  force  acting  through  long  periods,  and 
an  intense  force  acting  through  short  ones,  may  produce 
approximately  the  same  results.  To  Dr.  Hooker  I  have 


NIAGARA.  236 

been  indebted  for  some  specimens  of  stones,  the  first 
examples  of  which  were  picked  up  by  Mr.  Hnckworth  on 
the  shores  of  I/yell's  Bay,  near  Wellington,  in  New  Zealand. 
They  were  described  by  Mr.  Travers  in  the  '  Transactions 
of  the  New  Zealand  Institute.'  Unacquainted  with  their 
origin,  you  would  certainly  ascribe  their  forms  to  human 
workmanship.  They  resemble  knives  and  spear-heads, 
being  apparently  chiselled  off  into  facets,  with  as  much 
attention  to  symmetry  as  if  a  tool,  guided  by  human  in- 
telligence, had  passed  over  them.  But  no  human  instru- 
ment has  been  brought  to  bear  upon  these  stones.  They 
have  been  wrought  into  their  present  shape  by  the  wind- 
blown sand  of  I/yell's  Bay.  Two  winds  are  dominant  here, 
and  they  in  succession  urged  the  sand  against  opposite 
sides  of  the  stone ;  every  little  particle  of  sand  chipped 
away  its  infinitesimal  bit  of  stone,  and  in  the  end  sculptured 
these  singular  forms.1 

The  Sphynx  of  Egypt  is  nearly  covered  up  by  the  sand 
of  the  desert.  The  neck  of  the  Sphynx  is  partly  cut 
across,  not,  as  I  am  assured  by  Mr.  Huxley,  by  ordinary 
weathering,  but  by  the  eroding  action  of  the  fine  sand 

1  '  These  stones,  which  have  a  strong  resemblance  to  works  of  human 
art,  occur  in  great  abundance,  and  of  various  sizes,  from  half-an-inch  to 
several  inches  in  length.  A  large  number  were  exhibited  showing  the 
various  forms,  which  are  those  of  wedges,  knives,  arrow-heads,  &c.,  and  all 
with  sharp  cutting  edges. 

'  Mr.  Travers  explained  that,  notwithstanding  their  artificial  appearance, 
these  stones  were  formed  by  the  cutting  action  of  the  wind-driven  sand,  as 
it  passed  to  and  fro  over  an  exposed  boulder-bank.  He  gave  a  minute 
account  of  the  manner  in  which  the  varieties  of  form  are  produced,  and  re- 
ferred to  the  effect  which  the  erosive  action  thus  indicated  would  have  on 
railway  and  other  works  executed  on  sandy  tracts. 

•Dr.  Hector  stated  that  although,  as  a  group,  the  specimens  on  the  table 
could  not  well  be  mistaken  for  artificial  productions,  still  the  forms  are  so 
peculiar,  and  the  edges,  in  a  few  of  them,  so  perfect,  that  if  they  were  dis- 
covered associated  with  human  works,  there  is  no  doubt  that  they  would 
have  been  referred  to  the  so-called  "  stone  period." ' — Extracted  from  the 
Minutes  of  the  Wellington  Philosophical  Society,  February  9,  1869. 


236  FRAGMENTS   OF   SCIENCE. 

blown  against  it.  In  these  cases  Nature  furnishes  us  with 
hints  which  may  he  taken  advantage  of  in  art ;  and  this 
action  of  sand  has  been  recently  turned  to  extraordinary 
account  in  the  United  States.  When  in  Boston,  I  was 
taken  by  Mr.  Josiah  Quincey  to  see  the  action  of  the 
sand-blast.  A  kind  of  hopper  containing  fine  silicious 
sand  was  connected  with  a  reservoir  of  compressed  air, 
the  pressure  being  variable  at  pleasure.  The  hopper 
ended  in  a  long  slit,  from  which  the  sand  was  blown.  A 
plate  of  glass  was  placed  beneath  this  slit,  and  caused  to 
pass  slowly  under  it ;  it  came  out  perfectly  depolished, 
with  a  bright  opalescent  glimmer,  such  as  could  only  be 
produced  by  the  most  careful  grinding.  Every  little 
particle  of  sand  urged  against  the  glass,  having  all  its 
energy  concentrated  on  the  point  of  impact,  formed  there 
a  little  pit,  the  depolished  surface  consisting  of  innumerable 
hollows  of  this  description. 

But  this  was  not  all.  By  protecting  certain  portions  of 
the  surface,  and  exposing  others,  figures  and  tracery  of  any 
required  form  could  be  etched  upon  the  glass.  The  figures 
of  open  iron-work  could  be  thus  copied ;  while  wire-gauze 
placed  over  the  glass  produced  a  reticulated  pattern.  But 
it  required  no  such  resisting  substance  as  iron  to  shelter 
the  glass.  The  patterns  of  the  finest  lace  could  be  thus 
reproduced  ;  the  delicate  filaments  of  the  lace  itself  offering 
a  sufficient  protection.  All  these  effects  have  been  obtained 
with  a  simple  model  of  the  sand-blast  devised  by  my 
assistant.  A  fraction  of  a  minute  suffices  to  etch  upon 
glass  a  rich  and  beautiful  lace  pattern.  Any  yielding 
substance  may  be  employed  to  protect  the  glass.  By 
immediately  diffusing  the  shock  of  the  particle,  such  sub- 
stances practically  destroy  the  local  erosive  power.  The 
hand  can  bear,  without  inconvenience,  a  sand-shower  which 
would  pulverise  glass.  Etchings  executed  on  glass  with 
suitable  kinds  of  ink  are  accurately  worked  out  by  tho 


NIAGARA.  237 

sand-blast.  In  fact,  within  certain  limits,  the  harder  the 
surface,  the  greater  is  the  concentration  of  the  shock,  and 
the  more  effectual  is  the  erosion.  It  is  not  necessary 
that  the  sand  should  be  the  harder  substance  of  the  two ; 
corundum,  for  example,  is  much  harder  than  quartz  ;  still, 
quartz-sand  can  not  only  depolish,  but  actually  blow  a 
hole  through  a  plate  of  corundum.  Nay,  glass  may  be 
depolished  by  the  impact  of  fine  shot ;  the  grains  in  this 
case  bruising  the  glass,  before  they  have  time  to  flatten,  and 
turn  their  energy  into  heat. 

And  here,  in  passing,  we  may  tie  together  one  or  two 
apparently  unrelated  facts.  Supposing  you  turn  on,  at 
the  lower  part  of  a  house,  a  cock  which  is  fed  by  a  pipe 
from  a  cistern  at  the  top  of  the  house,  the  column  of 
water,  from  the  cistern  downwards,  is  set  in  motion.  By 
turning  off  the  cock,  this  motion  is  stopped ;  and  when 
the  turning  off  is  very  sudden,  the  pipe,  if  not  strong,  may 
be  burst  by  the  internal  impact  of  the  water.  By  distribu- 
ting the  turning  of  the  cock  over  half  a  second  of  time,  the 
shock  and  danger  of  rupture  may  be  entirely  avoided.  We 
have  here  an  example  of  the  concentration  of  energy  in  time. 
The  sand-blast  illustrates  the  concentration  of  energy  in 
space.  The  action  of  flint  and  steel  is  an  illustration  of  the 
same  principle.  The  heat  required  to  generate  the  spark 
is  intense;  and  the  mechanical  action,  being  moderate, 
must,  to  produce  fire,  be  in  the  highest  degree  con- 
centrated. This  concentration  is  secured  by  the  collision 
of  hard  substances.  Calc-spar  will  not  supply  the  place 
of  flint,  nor  lead  the  place  of  steel,  in  the  production  of  fire 
by  collision.  With  the  softer  substances,  the  total  heat 
produced  may  be  greater  than  with  the  hard  ones,  but,  to 
produce  the  spark,  the  heat  must  be  intensely  localised. 

But  we  can  go  far  beyond  the  mere  depolishing  of 
glass ;  indeed,  I  have  already  said  that  quartz-sand  can 
wear  a  hole  througb  corundum.  This  leads  me  to  express 


238  FRAGMENTS   OF   SCIENCE 

my  acknowledgments  to  General  Tilghman,1  who  is  the 
inventor  of  the  sand-blast.  To  his  spontaneous  kindness 
I  am  indebted  for  some  beautiful  illustrations  of  his 
process.  In  one  thick  plate  of  glass  a  figure  has  been 
worked  out  to  a  depth  of  |ths  of  an  inch.  A  second  plate, 
|ths  of  an  inch  thick,  is  entirely  perforated.  Through  a 
circular  plate  of  marble,  nearly  half  an  inch  thick,  open 
work  of  the  most  intricate  and  elaborate  description  has 
been  executed.  It  would  probably  take  many  days  to  per- 
form this  work  by  any  ordinary  process  ;  with  the  sand- 
blast it  was  accomplished  in  an  hour.  So  much  for  the 
strength  of  the  blast ;  its  delicacy  is  illustrated  by  a 
beautiful  example  of  line  engraving,  etched  on  glass  by 
means  of  the  blast.2 

This  power  of  erosion,  so  strikingly  displayed  when 
sand  is  urged  by  air,  renders  us  better  able  to  conceive  its 
action  when  urged  by  water.  The  erosive  power  of  a 
river  is  vastly  augmented  by  the  solid  matter  carried  along 
with  it.  Sand  or  pebbles,  caught  in  a  river  vortex,  can 
wear  away  the  hardest  rock  ;  '  potholes  '  and  deep  cylin- 
drical shafts  being  thus  produced.  An  extraordinary  in- 
stance of  this  kind  of  erosion  is  to  be  seen  in  the  Val 
Tournanche,  above  the  village  of  this  name.  The  gorge  at 
Handeck  has  been  thus  cut  out.  Such  waterfalls  were  once 
frequent  in  the  valleys  of  Switzerland ;  for  hardly  any 
valley  is  without  one  or  more  transverse  barriers  of  resist- 
ing material,  over  which  the  river  flowing  through  the 

1  The  absorbent  power,  if  I  may  use  the  phrase,  exerted  by  the  indus- 
trial arts  in  the  United  States,  is  forcibly  illustrated  by  the  rapid  transfer 
of  men  like  Mr.  Tilghman  from  the  life  of  the  soldier  to  that  of  the  civilian. 
General  McClellan,  now  a  civil    ngineer,  whom  I  had  the  honour  of  fre- 
quently meeting  in  New  York,  is  a  most  eminent  example  of  the  same  kind. 
At  the  end  of  the  war,  indeed,  a  million  and  a  half  of  men  were  thus  drawn, 
in  an  astonishingly  short  time,  from  military  to  civil  life.     It  is  obvious 
that  a  nation  with  these  tendencies  can  have  no  desire  for  war. 

2  The  sand-blast  will   be  in  operation  this  year  at  the  Kensington 
International  Exhibition. 


NIAGARA.  239 

valley  once  fell  as  a  cataract.  Near  Pontresina,  in  the 
Engadin,  there  is  such  a  case  ;  a  hard  gneiss  being  there 
worn  away  to  form  a  gorge,  through  which  the  river  from 
the  Morteratsch  glacier  rushes.  The  barrier  of  the  Kirchet 
above  Meyringen  is  also  a  case  in  point.  Behind  it  was  a 
lake,  derived  from  the  glacier  of  the  Aar,  and  over  the 
}>arrier  the  lake  poured  its  excess  of  water.  Here  the 
rock,  being  limestone,  was  in  great  part  dissolved ;  but 
added  to  this  we  had  the  action  of  the  sand  particles 
carried  along  by  the  water,  each  of  which,  as  it  struck  the 
rock,  chipped  it  away  like  the  particles  of  the  sand-blast. 
Thus,  by  solution  and  mechanical  erosion,  the  great  chasm 
of  the  Fiensteraarschlucht  was  formed.  It  is  demonstrable 
that  the  water  which  flows  at  the  bottoms  of  such  deep 
fissures  once  flowed  at  the  level  of  what  is  now  their  edges, 
and  tumbled  down  the  lower  faces  of  the  barriers.  Almost 
every  valley  in  Switzerland  furnishes  examples  of  this 
kind ;  the  untenable  hypothesis  of  earthquakes,  once  so 
readily  resorted  to  in  accounting  for  these  gorges,  being 
now  for  the  most  part  abandoned.  To  produce  the  Canons 
of  Western  America,  no  other  cause  is  needed  than  the  in- 
tegration of  effects  individually  infinitesimal. 

And  now  we  come  to  Niagara.  Soon  after  Europeans 
had  taken  possession  of  the  country,  the  conviction  appears 
to  have  arisen  that  the  deep  channel  of  the  river  Niagara 
below  the  falls  had  been  excavated  by  the  cataract.  In 
Mr.  Bakewell's  '  Introduction  to  Geology,'  the  prevalence 
of  this  belief  has  been  referred  to ;  it  is  expressed  thus  by 
Professor  Joseph  Henry  in  the  *  Transactions  of  the  Albany 
Institute : ' l  'In  viewing  the  position  of  the  falls,  and  the 
features  of  the  country  round,  it  is  impossible  not  to  be 
impressed  with  the  idea  that  this  great  natural  raceway 
has  been  formed  by  the  continued  action  of  the  irresistible 

•  Quoted  by  Bakewell. 


240  FRAGMENTS   OP  SCIENCE. 

Niagara,  and  that  the  falls,  beginning  at  Lewiston,  have, 
in  the  course  of  ages,  worn  back  the  rocky  strata  to  their 
present  site.'  The  same  view  is  advocated  by  Sir  Charles 
Lyell,  by  Mr.  Hall,  by  M.  Agassiz,  by  Professor  Kamsay, 
indeed  by  most  of  those  who  have  inspected  the  place. 

A  connected  image  of  the  origin  and  progress  of  the 
cataract  is  easily  obtained.  Walking  northward  from  the 
village  of  Niagara  Falls  by  the  side  of  the  river,  we  have 
to  our  left  the  deep  and  comparatively  narrow  gorge, 
through  which  the  Niagara  flows.  The  bounding  cliffs  of 
this  gorge  are  from  300  to  350  feet  high.  We  reach  the 
whirlpool,  trend  to  the  north-east,  and  after  a  little  time 
gradually  resume  our  northward  course.  Finally,  at  about 
seven  miles  from  the  present  falls,  we  come  to  the  edge  of 
a  declivity,  which  informs  us  that  we  have  been  hitherto 
walking  on  table-land.  At  some  hundreds  of  feet  below 
us  is  a  comparatively  level  plain,  which  stretches  to  Lake 
Ontario.  The  declivity  marks  the  end  of  the  precipitous 
gorge  of  the  Niagara.  Here  the  river  escapes  from  its 
steep  mural  boundaries,  and  in  a  widened  bed  pursues  its 
way  to  the  lake  which  finally  receives  its  waters. 

The  fact  that  in  historic  times,  even  within  the  memory 
of  man,  the  fall  has  sensibly  receded,  prompts  the  question, 
How  far  has  this  recession  gone  ?  At  what  point  did  the 
ledge  which  thus  continually  creeps  backwards  begin  its 
retrograde  course  9  To  minds  disciplined  in  such  researches 
the  answer  has  been,  and  will  be — At  the  precipitous  de- 
clivity which  crossed  the  Niagara  from  Lewiston  on  the 
American  to  Queenston  on  the  Canadian  side.  Over  this 
transverse  barrier  the  united  affluents  of  all  the  upper  lakes 
once  poured  their  waters,  and  here  the  work  of  erosion 
began.  The  dam,  moreover,  was  demonstrably  of  sufficient 
height  to  cause  the  river  above  it  to  submerge  Goat  Island ; 
and  this  would  perfectly  account  for  the  finding  by  Sir 
Charles  Lyell,  Mr.  Hall,  and  others,  in  the  sand  and  gravel 


NIAGARA.  241 

of  the  island,  the  same  fluviatile  shells  as  are  now  found 
in  the  Niagara  Eiver  higher  up.  It  would  also  account 
for  those  deposits  along  the  sides  of  the  river,  the  discovery 
of  which  enabled  Lyell,  Hall,  and  Kamsay  to  reduce  to 
demonstration  the  popular  belief  that  the  Niagara  once 
flowed  through  a  shallow  valley. 

The  physics  of  the  problem  of  excavation,  which  I  made 
clear  to  my  mind  before  quitting  Niagara,  are  revealed  by 
a  close  inspection  of  the  present  Horseshoe  Fall.  We 
see  evidently  that  the  greatest  weight  of  water  bends 
over  the  very  apex  of  the  Horseshoe.  In  a  passage  in  his 
excellent  chapter  on  Niagara  Falls,  Mr.  Hall  alludes  to 
this  fact.  Here  we  have  the  most  copious  and  the  most 
violent  whirling  of  the  shattered  liquid;  here  the  most 
powerful  eddies  recoil  against  the  shale.  From  this  por- 
tion of  the  fall,  indeed,  the  spray  sometimes  rises  without 
solution  of  continuity  to  the  region  of  clouds,  becoming 
gradually  more  attenuated,  and  passing  finally  through 
the  condition  of  true  cloud  into  invisible  vapour,  which  is 
sometimes  reprecipitated  higher  up.  All  the  phenomena 
point  distinctly  to  the  centre  of  the  river  as  the  place  of 
greatest  mechanical  energy,  and  from  the  centre  the  vigour 
of  the  fall  gradually  dies  away  towards  the  sides.  The 
Horseshoe  form,  with  the  concavity  facing  downwards,  is 
an  obvious  and  necessary  consequence  of  this  action.  Eight 
along  the  middle  of  the  river  the  apex  of  the  curve  pushes 
its  way  backwards,  cutting  along  the  centre  a  deep  and 
comparatively  narrow  groove,  and  draining  the  sides  as  it 
passes  them.1  Hence  the  remarkable  discrepancy  between 
the  widths  of  the  Niagara  above  and  below  the  Horseshoe. 
All  along  its  course,  from  Lewiston  Heights  to  its  present 
position,  the  form  of  the  fall  was  probably  that  of  a  horse- 

1  In  the  discourse  the  excavation  of  the  centre  and  drainage  of<  the  sides 
action  was  illustrated  by  a  model  devised  by  my  assistant,  Mr.  John 
Cottrell. 


242  FRAGMENTS   OF   SCIENCE. 

shoe  ;  for  this  is  merely  the  expression  of  the  greater  depth, 
and  consequently  greater  excavating  power,  of  the  centre 
of  the  river.  The  gorge,  moreover,  varies  in  width,  as  the 
depth  of  the  centre  of  the  ancient  river  varied,  being 
narrowest  where  that  depth  was  greatest. 

The  vast  comparative  erosive  energy  of  the  Horseshoe 
Fall  comes  strikingly  into  view  when  it  and  the  American 
Fall  are  compared  together.  The  American  branch  of  the 
upper  river  is  cut  at  a  light  angle  by  the  gorge  of  the 
Niagara.  Here  the  Horseshoe  Fall  was  the  real  excavator. 
ft  cut  the  rock,  and  formed  the  precipice,  over  which  the 
American  Fall  tumbles.  But  since  its  formation,  the  ero- 
sive action  of  the  American  Fall  has  been  almost  nil, 
while  the  Horseshoe  has  cut  its  way  for  500  yards  across 
the  end  of  Goat  Island,  and  is  now  doubling  back  to  ex- 
cavate its  channel  parallel  to  the  length  of  the  island. 
This  point,  which  impressed  me  forcibly,  has  not,  I  have 
just  learned,  escaped  the  acute  observation  of  Professor 
Eamsay.1  The  river  bends ;  the  Horseshoe  immediately  ac- 
commodates itself  to  the  bending,  and  will  follow  implicitly 
the  direction  of  the  deepest  water  in  the  upper  stream. 
The  flexibility  of  the  gorge,  if  I  may  use  the  term,  is  de- 
termined by  the  flexibility  of  the  river  channel  above  it. 
Were  the  Niagara  centre  above  the  fall  sinuous,  the  gorge 
would  obediently  follow  its  sinuosities.  Once  suggested,  no 
doubt  geographers  will  be  able  to  point  out  many  examples 
of  this  action.  The  Zambesi  is  thought  to  present  a  great 
difficulty  to  the  erosion  theory,  because  of  the  sinuosity 
of  the  chasm  below  the  Victoria  Falls.  But,  assuming  the 
basalt  to  be  of  tolerably  uniform  texture,  had  the  river 

1  His  words  are  :  '  Where  the  body  of  water  is  small  in  the  American 
Fall,  the  edge  has  only  receded  a  few  yards  (where  most  eroded)  during  the 
time  that  the  Canadian  Fall  has  receded  from  the  north  corner  of  Gait 
Island  to  the  innermost  curve  of  the  Horseshoe  Fall.' — Quarterly  Journal 
of  Geological  Society,  May  1859. 


NIAGARA..  243 

been  examined  before  the  formation  of  this  sinuous  channel,  - 
the  present  zigzag  course  of  the  gorge  below  the  fall  could, 
I  am  persuaded,  have  been  predicted,  while  the  sounding 
of  the  present  river  would  enable  us  to  predict  the  course 
to  be  pursued  by  the  erosion  in  the  future. 

But  not  only  has  the  Niagara  Eiver  cut  the  gorge ;  it 
lias  carried  away  the  chips  of  its  own  workshop.  The 
ehale,  being  probably  crumbled,  is  easily  carried  away. 
But  at  the  base  of  the  fall  we  find  the  huge  boulders 
already  described,  and  by  some  means  or  other  these  are 
removed  down  the  river.  The  ice  which  fills  the  gorge  in 
winter,  and  which  grapples  with  the  boulders,  has  been 
regarded  as  the  transporting  agent.  Probably  it  is  so  to 
some  extent.  But  erosion  acts  without  ceasing  on  the 
abutting  points  of  the  boulders,  thus  withdrawing  their 
support  and  urging  them  gradually  down  the  river.  So- 
lution also  does  its  portion  of  the  work.  That  solid  matter 
is  carried  down  is  proved  by  the  difference  of  depth  between 
the  Niagara  Kiver  and  Lake  Ontario,  where  the  river  enters 
it.  The  depth  falls  from  72  feet  to  20  feet,  in  consequence 
of  the  deposition  of  solid  matter  caused  by  the  diminished 
motion  of  the  river.1 

The  accompanying  highly  instructive  map  has  been 
reduced  from  one  published  in  Mr.  Hall's  '  Geology  of 
New  York.'  It  is  based  on  surveys  executed  in  1842,  by 
Messrs.  Gibson  and  Evershed.  The  ragged  edge  of  the 
American  Fall  north  of  Goat  Island  marks  the  amount  of 
erosion  which  it  has  been  able  to  accomplish,  while  the 
Horseshoe  Fall  was  cutting  its  way  southward  across  the 
end  of  Goat  Island  to  its  present  position.  The  American 
Fall  is  168  feet  high,  a  precipice  cut  down,  not  by  itself, 
but  by  the  Horseshoe  Fall.  The  latter  in  1842  was  159 
feet  high,  and,  as  shown  by  the  map,  is  already  turning 

1  Near  the  mouth  of  the  gorge  at  Queenston,  the  depth,  according  to 
the  Admiralty  Chart,  is  180  feet ;  well  within  the  gorge  it  is  132  feet. 
13 


COAT 
IS      LAND 


NIAGAKA.  246 

eastward,  to  excavate  its  gorge  along  the  centre  of  the 
upper  river,  p  is  the  apex  of  the  Horseshoe,  and  T  marks 
the  site  of  the  Terrapin  Tower,  with  the  promontory  ad- 
jacent, round  which  I  was  conducted  by  Conroy.  Pro- 
bably since  1842  the  Horseshoe  has  worked  back  beyond  the 
position  here  assigned  to  it. 

In  conclusion,  we  may  say  a  word  regarding  the  proxi- 
mate future  of  Niagara.  At  the  rate  of  excavation  assigned 
to  it  by  Sir  Charles  Lyell,  namely,  a  foot  a  year,  five  thou- 
sand years  or  so  will  carry  the  Horseshoe  Fall  far  higher 
than  Goat  Island.  As  the  gorge  recedes  it  will  drain,  as 
it  has  hitherto  done,  the  banks  right  and  left  of  it,  thus 
leaving  a  nearly  level  terrace  between  Goat  Island  and  the 
edge  of  the  gorge.  Higher  up  it  will  totally  drain  the 
American  branch  of  the  river ;  the  channel  of  which  in 
due  time  will  become  cultivable  land.  The  American 
Fall  will  then  be  transformed  into  a  dry  precipice,  forming 
a  simple  continuation  of  the  cliffy  boundary  of  the  Niagara. 
At  the  place  occupied  by  the  fall  at  this  moment  we  shall 
have  the  gorge  enclosing  a  right  angle,  a  second  whirlpool 
being  the  consequence  of  this.  To  those  who  visit  Niagara 
a  few  millenniums  hence  I  leave  the  verification  of  this 
prediction.  All  that  can  be  said  is,  that  if  the  causes  now 
in  action  continue  to  act,  it  will  prove  itself  literally  true. 


246  FRAGMENTS   OP   SCIENCE 


VIII. 

LIFE  AND  LETTERS  OF  FARADAY. 
1870. 

UNDERTAKEN  and  executed  in  a  reverent  and  loving 
spirit,  the  work  of  Dr.  Bence  Jones  makes  Faraday 
the  virtual  writer  of  his  own  life.  Everybody  now  knows 
the  story  of  the  philosopher's  birth  ;  that  his  lather  was  a 
smith;  that  he  was  born  at  Newington  Butts  in  1791; 
that  he  ran  along  the  London  pavements,  a  bright-eyed 
errand  boy,  with  a  load  of  brown  curls  upon  his  head  and 
a  packet  of  newspapers  under  his  arm ;  that  the  lad's 
master  was  a  bookseller  and  bookbinder — a  kindly  man, 
who  became  attached  to  the  little  fellow,  and  in  due  time 
made  him  his  apprentice  without  fee ;  that  during  his 
apprenticeship  he  found  his  appetite  for  knowledge  pro- 
voked and  strengthened  by  the  books  he  stitched  and 
covered.  Thus  he  grew  in  wisdom  and  stature  to  his 
year  of  legal  manhood,  when  he  appears  in  the  volumes 
before  us  as  a  writer  of  letters,  which  reveal  his  occupa- 
tion, acquirements,  and  tone  of  mind.  His  correspondent 
was  Mr.  Abbott,  a  member  of  the  Society  of  Friends,  who, 
with  a  forecast  of  his  correspondent's  greatness,  preserved 
his  letters  and  produced  them  at  the  proper  time. 

In  later  years  Faraday  always  carried  in  his  pocket  a 
blank  card,  on  which  he  jotted  down  in  pencil  his  thoughts 
and  memoranda.  He  made  his  notes  in  the  laboratory,  in 
the  theatre,  and  in  the  streets.  This  distrust  of  his 
memory  reveals  itself  in  his  first  letter  to  Abbott.  To  a 


FARADAY.  247 

proposition  that  no  new  enquiry  should  be  started  between 
them  before  the  old  one  had  been  exhaustively  discussed, 
Faraday  objects.  « Your  notion,'  he  says,  « I  can  hardly 
allow,  for  the  following  reason  :  ideas  and  thoughts  spring 
up  in  toy  mind  which  are  irrevocably  lost  for  want  of 
noting  at  the  time.'  Gentle  as  he  seemed,  he  wished  to 
have  his  own  way,  and  he  had  it  throughout  his  life. 
Differences  of  opinion  sometimes  arose  between  the  two 
friends,  and  then  they  resolutely  faced  each  other.  '  I  ac- 
cept your  offer  to  fight  it  out  with  joy,  and  shall  in  the 
battle  of  experience  cause  not  pain,  but,  I  hope,  pleasure.' 
Faraday  notes  his  own  impetuosity,  and  incessantly  checks 
it.  There  is  at  times  something  mechanical  in  his  self- 
restraint.  In  another  nature  it  would  have  hardened  into 
mere  '  correctness '  of  conduct ;  but  his  overflowing  affec- 
tions prevented  this  in  his  case.  The  habit  of  self-control 
became  a  second  nature  to  him  at  lagt,  and  lent  serenity 
to  his  later  years. 

In  October  1812  he  was  engaged  by  a  Mr.  De  la 
Roche  as  a  journeyman  bookbinder ;  but  the  situation  did 
not  suit  him.  His  master  appears  to  have  been  an  aus- 
tere and  passionate  man,  and  Faraday  was  to  the  last 
degree  sensitive.  All  his  life  he  continued  so.  He  suf- 
fered at  times  from  dejection ;  and  a  certain  grimness,  too, 
pervaded  his  moods.  '  At  present,'  he  writes  to  Abbott,  '  J. 
am  as  serious  as  you  can  be,  and  would  not  scruple  to 
speak  a  truth  to  any  human  being,  whatever  repugnance 
it  might  give  rise  to.  Being  in  this  state  of  mind,  I 
should  have  refrained  from  writing  to  you,  did  I  not  con- 
ceive from  the  general  tenor  of  your  letters  that  your 
mind  is,  at  proper  times,  occupied  upon  serious  subjects 
to  the  exclusion  of  those  that  are  frivolous.'  Plainly 
he  had  fallen  into  that  stern  Puritan  mood,  which  not 
only  crucifies  the  affections  and  lusts  of  him  who  har- 


248  FRAGMENTS   OF  SCIENCE. 

hours  it,  but  is  often  a  cause  of  disturbed  digestion  to  his 
friends. 

About  three  months  after  his  engagement  with  De  la 
Roche,  Faraday  quitted  him  and  bookbinding  together. 
He  had  heard  Davy,  ccpied  his  lectures,  and  written  to 
him,  entreating  to  be  released  from  Trade,  which  he  hated, 
and  enabled  to  pursue  Science.  Davy  recognised  the 
merit  of  his  correspondent,  kept  his  eye  upon  him,  and, 
when  occasion  offered,  drove  to  his  door  and  sent  in  a 
letter,  offering  him  the  post  of  assistant  in  the  labora- 
tory of  the  Royal  Institution.  He  was  engaged  March  1, 
1812,  and  on  the  8th  we  find  him  extracting  the  sugar 
from  beet-root.  He  joined  the  City  Philosophical  Society 
which  had 'been  founded  by  Mr.  Tatum  in  1808.  'The 
discipline  was  very  sturdy,  the  remarks  very  plain,  and 
the  results  most  valuable.'  Faraday  derived  great  profit 
from  this  little  association.  In  the  laboratory  he  had  a 
discipline  sturdier  still.  Both  Davy  and  himself  were  at 
this  time  frequently  cut  and  bruised  by  explosions  of  chlo- 
ride of  nitrogen.  One  explosion  was  so  rapid  '  as  to  blow 
my  hand  open,  tear  away  a  part  of  one  nail,  and  make  my 
fingers  so  sore  that  I  cannot  use  them  easily.'  In  another 
experiment  '  the  tube  and  receiver  were  blown  to  pieces,  I 
got  a  cut  on  the  head,  and  Sir  Humphry  a  bruise  on 
his  hand.'  And  again  speaking  of  the  same  substance,  he 
says,  « when  put  in  the  pump  and  exhausted,  it  stood  for 
a  moment,  and  then  exploded  with  a  fearful  noise.  Both 
Sir  H.  and  I  had  masks  on,  but  I  escaped  this  time  the 
best.  Sir  H.  had  his  face  cut  in  two  places  about  the 
chin,  and  a  violent  blow  on  the  forehead  struck  through  a 
considerable  thickness  of  silk  and  leather.'  It  was  this 
same  substance  that  blew  out  the  eye  of  Dulong. 

Over  and  over  again,  even  at  this  early  date,  we  can 
discern  the  quality  whicn,  compounded  with  his  rare  intel- 
lectual power,  made  him  a  great  experimental  philosopher. 


FAEADAT.  249 

This  was  his  desire  to  see  facts,  and  not  to  rest  contented 
with  the  descriptions  of  them.  He  frequently  pits  the 
eye  against  the  ear,  and  affirms  the  enormous  superiority 
of  the  organ  of  vision.  Late  in  life  I  have  heard  him  say 
that  he  could  never  fully  understand  an  experiment  until 
he  had  seen  it.  But  he  did  not  confine  himself  to  experi- 
ment. He  aspired  to  he  a  teacher,  and  reflected  and 
wrote  upon  the  method  of  scientific  exposition.  '  A  lec- 
turer,' he  observes,  *  should  appear  easy  and  collected,  un- 
daunted and  unconcerned  : '  still  '  his  whole  behaviour 
should  evince  respect  for  his  audience.'  These  recommend- 
ations were  afterwards  in  great  part  embodied  by  himself. 
I  doubt  his  '  unconcern,'  but  his  fearlessness  was  often 
manifested.  It  used  to  rise  within  him  as  a  wave,  which 
carried  both  him  and  his  audience  along  with  it.  On  rare 
occasions  also,  when  he  felt  himself  and  his  subject  hope- 
lessly unintelligible,  he  suddenly  evoked  a  certain  reckless- 
ness of  thought,  and,  without  halting  to  extricate  his  bewil- 
dered followers,  he  would  dash  alone  through  the  jungle 
into  which  he  had  unwittingly  led  them ;  thus  saving 
them  from  ennui  by  the  exhibition  of  a  vigour  which,  for 
the  time  being,  they  could  neither  share  nor  comprehend. 
In  October  1813  he  quitted  England  with  Sir  Hum- 
phry and  Lady  Davy.  During  his  absence  he  kept  a 
journal,  from  which  copious  and  interesting  extracts  have 
been  made  by  Dr.  Bence  Jones.  Davy  was  considerate, 
preferring  at  times  to  be  his  own  servant  rather  than  im- 
pose on  Faraday  duties  which  he  disliked.  But  Lady 
Davy  was  the  reverse.  She  treated  him  as  an  underling ; 
he  chafed  under  the  treatment,  and  was  often  on  the  point 
of  returning  home.  They  halted  at  Geneva.  De  la  Rive, 
the  elder,  had  known  Davy  in  1799,  and,  by  his  writings  in 
the  4  Bibliotheque  Britannique,'  had  been  the  first  to  make 
the  English  chemist's  labours  known  abroad.  He  wel- 
comed Davy  to  his  country  residence  in  1814.  Both  were 


250  FRAGMENTS   OF  SCIENCE. 

sportsmen,  and  they  often  went  out  shooting  together. 
On  these  occasions  P'araday  charged  Davy's  gun  while  De 
la  Eive  charged  his  own.  Once  the  Genevese  philosopher 
found  himself  by  the  side  of  Faraday,  and  in  his  frank 
and  genial  way  entered  into  conversation  with  the  young 
man.  It  was  evident  that  a  person  possessing  such  a 
charm  of  manner  and  such  high  intelligence  could  be  no 
mere  servaut.  On  enquiiy  De  la  Eive  was  somewhat 
shocked  to  find  that  the  soi-disant  domestique  was  really 
preparateur  in  the  laboratory  of  the  Royal  Institution ;  and 
he  immediately  proposed  that  Faraday  thenceforth  should 
join  the  masters  instead  of  the  servants  at  their  meals. 
To  this  Davy,  probably  out  of  weak  deference  to  his  wife, 
objected;  but  an  arrangement  was  come  to  that  Faraday 
thenceforward  should  have  his  food  in  his  own  room. 
Rumour  states  that  a  dinner  in  honour  of  Faraday  was 
given  by  De  la  Rive.  This  is  a  delusion  ;  there  was  no 
such  banquet ;  but  Faraday  never  forgot  the  kindness  of 
the  friend  who  saw  his  merit  when  he  was  a  mere  gar f on 
de  laboratoire.1 

He  returned  in  1815  to  the  Royal  Institution.  Here 
he  helped  Davy  for  years ;  he  worked  also  for  himself,  and 
lectured  frequently  •  at  the  City  Philosophical  Society. 
He  took  lessons  in  elocution,  happily  without  damage  to 
his  natural  force,  earnestness,  and  grace  of  delivery.  He 
was  never  pledged  to  theory,  and  he  changed  in  opinion 
as  knowledge  advanced.  With  him  life  was  growth.  In 
those  early  lectures  we  hear  him  say,  *  In  knowledge,  that 
man  only  is  to  be  contemned  and  despised  who  is  not  in  a 

1  While  confined  last  autumn  at  Geneva  by  the  effects  of  a  fall  in  the 
Alps,  my  friends,  with  a  kindness  I  can  never  forget,  did  all  that  friendship 
could  suggest  to  render  my  captivity  pleasant  to  me.  M.  de  la  Rive  then 
wrote  out  for  me  the  full  account,  of  which  the  foregoing  is  a  condensed 
abstract.  It  was  at  the  desire  of  Dr.  Bence  Jones  that  I  asked  him  to  do 
so.  The  rumour  of  a  banquet  at  Geneva  illustrates  the  tendency  to  sub- 
stitute for  the  youth  of  1814  the  Faraday  of  later  years. 


FARADAY.  251 

state  of  transition.'  And  again  :  '  Nothing  is  more  diffi- 
cult and  requires  more  caution  than  philosophical  deduc- 
tion, nor  is  there  anything  more  adverse  to  its  accuracy 
than  fixity  of  opinion.'  Not  that  lie  was  wafted  about  by 
every  wind  of  doctrine;  but  that  he  united  flexibility 
with  his  strength.  In  striking  contrast  with  this  intel- 
lectual expansiveness  was  his  fixity  in  religion,  but  this  is 
a  subject  which  cannot  be  discussed  here. 

Of  all  the  letters  published  in  these  volumes  none 
possess  a  greater  charm  than  those  of  Faraday  to  his  wife. 
Here,  as  Dr.  Bence  Jones  truly  remarks,  'he  laid 
open  all  his  mind  and  the  whole  of  his  character,  and 
what  can  be  made  known  can  scarcely  fail  to  charm  every 
one  by  its  loveliness,  its  truthfulness,  and  its  earnestness.' 
Abbott  and  he  sometimes  swerved  into  word-play  about 
love ;  but  up  to  1820,  or  thereabouts,  the  passion  was 
potential  merely.  Faraday's  journal  indeed  contains  en- 
tries which  show  that  he  took  pleasure  in  the  assertion  of 
his  contempt  for  love;  but  these  very  entries  became 
links  in  his  destiny.  It  was  through  them  that  he 
became  acquainted  with  one  who  inspired  him  with  a 
feeling  which  only  ended  with  his  life.  His  biographer 
has  given  us  the  means  of  tracing  the  varying  moods 
which  preceded  his  acceptance.  They  reveal  more  than 
the  common  alternations  of  light  and  gloom  ;  at  one 
moment  he  wishes  that  his  flesh  might  melt  and  he  be- 
come nothing;  at  another  he  is  intoxicated  with  hope. 
The  impetuosity  of  his  character  was  then  unchastened  by 
the  discipline  to  which  it  was  subjected  in  after-years. 
The  very  strength  of  his  passion  proved  for  a  time  a  bar 
to  its  advance,  suggesting,  as  it  did,  to  the  conscientious 
mind  of  Miss  Barnard,  doubts  of  her  capability  to  return 
it  with  adequate  force.  But  they  met  again  and  again, 
and  at  each  successive  meeting  he  found  his  heaven 
clearer,  until  at  length  he  was  able  to  say,  *  Not  a 


262  FRAGMENTS   OF   SCIENCE. 

moment's  alloy  of  this  evening's  happiness  occurred. 
Everything  was  delightful  to  the  last  moment  of  my  stay 
with  my  companion,  because  she  was  so.'  The  turbulence 
of  doubt  subsided,  and  a  calm  and  elevating  confidence 
took  its  place.  '  What  can  I  call  myself,'  he  writes  to  her 
in  a  subsequent  letter,  '  to  convey  most  perfectly  my  affec- 
tion and  love  for  you  ?  Can  I  or  can  truth  say  more  than 
that  for  this  world  I  am  yours  ?'  Assuredly  he  made  his 
profession  good,  and  no  fairer  light  falls  upon  his  cha- 
racter than  that  which  reveals  his  relations  to  his  wife. 
Never,  I  believe,  existed  a  manlier,  purer,  steadier  love. 
Like  a  burning  diamond,  it  continued  to  shed,  fot  six-and- 
forty  years,  its  white  and  smokeless  glow. 

Faraday  was  married  on  June  12,  1821  ;  and  up  to 
this  date  Davy  appears  throughout  as  his  friend.  Soon 
afterwards,  however,  disunion  occurred  between  them, 
which,  while  it  lasted,  must  have  given  Faraday  intense 
pain.  It  is  impossible  to  doubt  the  honesty  of  conviction 
with  which  this  subject  has  been  treated  by  Dr.  Bence 
Jones,  and  there  may  be  facts  known  to  him,  but  not  ap- 
pearing in  these  volumes,  which  justify  his  opinion  that 
Davy  in  those  days  had  become  jealous  of  Faraday.  This, 
which  is  the  prevalent  belief,  is  also  reproduced  in  an 
excellent  article  in  the  March  number  of  '  Fraser's  Maga- 
zine.' But  the  best  analysis  I  can  make  of  the  data  fails 
to  present  Davy  in  this  light  to  me.  The  facts,  as  I  regard 
them,  are  briefly  these. 

In  1820,  Oersted  of  Copenhagen  made  the  celebrated 
discovery  which  connects  electricity  with  magnetism,  and 
immediately  afterwards  the  acute  mind  of  Wollaston  per- 
ceived that  a  wire  carrying  a  current  ought  to  rotate 
round  its  own  axis  under  the  influence  of  a  magnetic  pole. 
In  1821  he  tried,  but  failed,  to  realise  this  result  in  the 
laboratory  of  the  Royal  Institution.  Faraday  was  not 
present  at  the  moment,  but  he  came  in  immediately  after- 


FARADAY.  253 

wards  and  heard  the  conversation  of  Wollaston  and  Davy 
about  the  experiment.  He  had  also  heard  a  rumour  of  a 
wager  that  Dr.  Wollaston  would  eventually  succeed. 

This  was  in  April.  In  the  autumn  of  the  same  year 
Faraday  wrote  a  history  of  electro-magnetism,  and  repeated 
for  himself  the  experiments  which  he  described.  It  was 
while  thus  instructing  himself  that  he  succeeded  in  causing 
a  wire,  carrying  an  electric  current,  to  rotate  round  a  mag- 
netic pole.  This  was  not  the  result  sought  by  Wollaston, 
but  it  was  closely  related  to  that  result. 

The  strong  tendency  of  Faraday's  mind  to  look  upon 
the  reciprocal  actions  of  natural  forces  gave  birth  to  his 
greatest  discoveries ;  and  we,  who  know  this,  should  be 
justified  in  concluding  that,  even  had  Wollaston  not  pre- 
ceded him,  the  result  would  have  been  the  same.  But  in 
judging  Davy  we  ought  to  transport  ourselves  to  his  time, 
and  carefully  exclude  from  our  thoughts  and  feelings  that 
noble  subsequent  life,  which  would  render  simply  impos- 
sible the  ascription  to  Faraday  of  anything  unfair.  It 
would  be  unjust  to  Davy  to  put  our  knowledge  in  the 
place  of  his,  or  to  credit  him  with  data  which  he  could 
not  have  possessed.  Eumour  and  fact  had  connected  the 
name  of  Wollaston  with  these  supposed  interactions 
between  magnets  and  currents.  When,  therefore,  Faraday 
in  October  published  his  successful  experiment,  without 
any  allusion  to  Wollaston,  general,  though  really  un- 
grounded, criticism  followed.  I  say  ungrounded  because, 
firstly,  Faraday's  experiment  was  not  that  of  Wollaston, 
and  secondly,  Faraday,  before  he  published  it,  had  actually 
called  upon  Wollaston,  and  not  finding  him  at  home  did 
not  feel  himself  authorised  to  mention  his  name. 

In  December,  Faraday  published  a  second  paper  on  the 
same  subject,  from  which,  through  a  misapprehension, 
the  name  of  Wollaston  was  also  omitted.  Wai-burton  and 
others  thereupon  affirmed  that  Wollaston's  ideas  had  been 


264  FRAGMENTS   OF   SCIENCE. 

appropriated  without  acknowledgment,  and  it  is  plain  that 
Wollaston  himself,  though  cautious  in  his  utterance,  was 
also  hurt.  Censure  grew  till  it  became  intolerable.  '  I 
hear,'  writes  Faraday  to  his  friend  Stodart,  '  every  day  more 
and  more  of  these  sounds,  which,  though  only  whispers  to 
me,  are,  I  suspect,  spoken  aloud  among  scientific  men.' 
He  might  have  written  explanations  and  defences,  but  he 
went  straighter  to  the  point.  He  wished  to  see  the  prin- 
cipals face  to  face — to  plead  his  cause  before  them  person- 
ally. There  was  a  certain  vehemence  in  his  desire  to  do  this. 
He  saw  Wollaston,  he  saw  Davy,  he  saw  Warburton  ;  and 
I  am  inclined  to  think  that  it  was  the  irresistible  candour 
and  truth  of  character  which  these  viva  voce  defences  re- 
vealed, as  much  as  the  defences  themselves,  that  disarmed 
resentment  at  the  time. 

As  regards  Davy,  another  cause  of  dissension  arose  in 
1823.  In  the  spring  of  that  year  Faraday  analysed  the 
hydrate  of  chlorine,  a  substance  once  believed  to  be  the 
element  chlorine,  but  proved  by  Davy  to  be  a  compound 
of  that  element  and  water.  The  analysis  was  looked  over 
by  Davy,  who  then  and  there  suggested  to  Faraday  to 
heat  the  hydrate  in  a  closed  glass  tube.  This  was  done, 
the  substance  was  decomposed,  and  one  of  the  products  of 
decomposition  was  proved  by  Faraday  to  be  chlorine 
liquefied  by  its  own  pressure.  On  the  day  of  its  discovery 
he  communicated  this  result  to  Dr.  Paris.  Davy,  on  being 
informed  of  it,  instantly  liquefied  another  gas  in  the  same 
way.  Having  struck  thus  into  Faraday's  enquiry,  ought 
he  not  to  have  left  the  matter  in  Faraday's  hands  ?  I 
think  he  ought.  But,  considering  his  relation  to  both 
Faraday  and  the  hydrate  of  chlorine,  Davy,  I  submit,  may 
be  excused  for  thinking  differently.  A  father  is  not 
always  wise  enough  to  see  that  his  son  has  ceased  to  be  a 
boy,  and  estrangement  on  this  account  is  not  rare  ;  nor 
was  Davy  wise  enough  to  discern  that  Faraday  had  passed 


FAEADAY.  256 

the  mere  assistant  stage,  and  become  a  discoverer.  It  is 
now  hard  to  avoid  magnifying  this  error.  But  had  Fara- 
day died  or  ceased  to  work  at  this  time,  or  had  his  subse- 
quent life  been  devoted  to  money-getting,  instead  of  to 
research,  would  anybody  now  dream  of  ascribing  jealousy 
to  Davy  ?  Assuredly  not.  Why  should  he  be  jealous  ? 
His  reputation  at  this  time  was  almost  without  a  parallel  : 
his  glory  was  without  a  cloud.  He  had  added  to  his  other 
discoveries  that  of  Faraday,  and  after  having  been  his 
teacher  for  seven  years,  his  language  to  him  was  this:  '  It 
gives  me  great  pleasure  to  hear  that  you  are  comfortable 
at  the  EoyaJ  Institution,  and  I  trust  that  you  will  not 
only  do  something  good  and  honourable  for  yourself,  but 
also  for  science.'  This  is  not  the  language  of  jealousy, 
potential  or  actual.  But  the  chlorine  business  introduced 
irritation  and  anger,  to  which,  and  not  to  any  ignobler 
motive,  Davy's  opposition  to  the  election  of  Faraday  to 
the  Eoyal  Society  is,  I  am  persuaded,  to  be  ascribed. 

These  matters  are  touched  upon  with  perfect  candour, 
and  becoming  consideration,  in  the  volumes  of  Dr.  Bence 
Jones  ;  but  in  '  society '  they  are  not  always  so  handled. 
Here  a  name  of  noble  intellectual  associations  is  surrounded 
by  injurious  rumours  which  I  would  willingly  scatter  for 
ever.  The  pupil's  magnitude,  and  the  splendour  of  his 
position,  are  too  great  and  absolute  to  need  as  a  foil  the 
humiliation  of  his  master.  Brothers  in  intellect,  Davy  and 
Faraday,  however,  could  never  have  become  brothers  in 
feeling ;  their  characters  were  too  unlike.  Davy  loved  the 
pomp  and  circumstance  of  fame  ;  Faraday  the  inner  con- 
sciousness that  he  had  fairly  won  renown.  They  were 
both  proud  men.  But  with  Davy  pride  projected  itself 
into  the  outer  world  ;  while  with  Faraday  it  became  a 
steadying  and  dignifying  inward  force.  In  one  great  par- 
ticular they  agreed.  Each  of  them  could  have  turned  his 
science  to  immense  commercial  profit,  but  neither  of  them 


256  FRAGMENTS    OF   SCIENCE. 

did  so.  The  noble  excitement  of  research,  and  the  delight 
of  discovery,  constituted  their  reward.  I  commend  them 
to  the  reverence  which  great  gifts  greatly  exercised  ought 
to  inspire.  They  were  both  ours  ;  and  through  the  coming 
centuries  England  will  be  able  to  point  with  just  pride  to 
the  possession  of  such  men. 


The  first  volume  of  the  '  Life  and  Letters '  reveals  to 
us  the  youth  who  was  to  be  father  to  the  man.  Skil- 
ful, aspiring,  resolute,  he  grew  steadily  in  knowledge  and 
in  power.  Consciously  or  unconsciously,  the  relation  of 
Action  to  Reaction  was  ever  present  to  Faraday's  mind. 
It  had  been  fostered  by  his  discovery  of  Magnetic  Rota- 
tions, and  it  planted  in  him  more  daring  ideas  of  a  similar 
kind.  Magnetism  he  knew  could  be  evoked  by  electricity, 
and  he  thought  that  electricity,  in  its  turn,  ought  to  be 
capable  of  evolution  by  magnetism.  On  August  29,  1831, 
his  experiments  on  this  subject  began.  He  had  been  forti- 
fied by  previous  trials,  which,  though  failures,  had  be- 
gotten instincts  directing  him  towards  the  truth.  He, 
like  every  strong  worker,  might  at  times  miss  the  outward 
object,  but  he  always  gained  the  inner  light,  education 
and  expansion.  Of  this  Faraday's  life  was  a  constant 
illustration.  By  November  he  had  discovered  and  colli- 
gated a  multitude  of  the  most  wonderful  and  unexpected 
phenomena.  He  had  generated  currents  by  currents ; 
currents  by  magnets,  permanent  and  transitory ;  and  he 
afterwards  generated  currents  by  the  earth  itself.  Arago's 
*  Magnetism  of  Rotation,'  which  had  for  years  offered  itself 
as  a  challenge  to  the  best  scientific  intellects  of  Europe, 
now  fell  into  his  hands.  It  proved  to  be  a  beautiful,  but 
still  special,  illustration  of  the  great  principle  of  Magneto- 
electric  Induction.  Nothing  equal  to  this,  in  the  way 


FABADAY.  257 

of    pure    experimental     enquiry,    had     previously    been 
achieved. 

Electricities  from  various  sources  were  next  examined, 
and  their  differences  and  resemblances  revealed.  He  thus 
assured  himself  of  their  substantial  identity.  He  then 
took  up  Conduction,  and  gave  many  striking  illustrations 
of  the  influence  of  Fusion  on  Conducting  Power.  Re- 
nouncing professional  work,  from  which  at  this  time  he 
might  have  derived  an  income  of  many  thousands  a  year, 
he  poured  his  whole  momentum  into  his  researches.  He 
was  long  entangled  in  Electro-chemistry.  The  light  of 
law  was  for  a  time  obscured  by  the  thick  umbrage  of  novel 
facts ;  but  he  finally  emerged  from  his  researches  with 
the  great  principle  of  Definite  Electro-chemical  Decom- 
position in  his  hands.  If  his  discovery  of  Magneto-elec- 
tricity may  be  ranked  with  that  of  the  Pile  by  Volta,  this 
new  discovery  may  almost  stand  beside  that  of  Definite 
Combining  Proportions  in  Chemistry.  He  passed  on  to 
Static  Electricity — its  Conduction,  Induction,  and  Mode 
of  Propagation.  He  discovered  and  illustrated  the  prin- 
ciple of  Inductive  capacity  ;  and,  turning  to  theory,  he 
asked  himself  how  electrical  attractions  and  repulsions  are 
transmitted.  Are  they,  like  gravity,  actions  at  a  distance, 
or  do  they  require  a  medium  ?  If  the  former,  then,  like 
gravity,  they  will  act  in  straight  lines ;  if  the  latter,  then, 
like  sound  or  light,  they  may  turn  a  corner.  Faraday 
held — and  his  views  are  gaining  ground — that  his  experi- 
ments proved  the  fact  of  curvilinear  propagation,  and 
hence  the  operation  of  a  medium.  Others  denied  this ; 
but  none  can  deny  the  profound  and  philosophic  character 
of  his  leading  thought.1  The  first  volume  of  the  Researches 
contains  all  the  papers  here  referred  to. 

1  In  a  very  remarkable  paper  published  in  Poggendorff 's  '  Annalen '  fot 
1857,  Werner  Siemens  accepts  and  develops  Faraday's  theory  of  Molecular 
Induction. 


258  FRAGMENTS   OP   SCIENCE. 

Faraday  had  heard  it  stated  that  henceforth  physical 
discoveries  would  be  made  solely  by  the  aid  of  mathematics; 
that  we  had  our  data,  and  needed  only  to  work  deductively. 
Statements  of  a  similar  character  crop  out  from  time  to 
time  in  our  day.  They  arise  from  an  imperfect  acquaint- 
ance with  the  nature,  present  condition,  and  prospective 
vastness  of  the  field  of  physical  enquiry.  The  tendency 
of  natural  science  doubtless  is  to  bring  all  physical  phe- 
nomena under  the  dominion  of  mechanical  laws  ;  to  give 
them,  in  other  words,  mathematical  expression.  But  our 
approach  to  this  result  is  asymptotic ;  and  for  ages  to 
come — possibly  for  all  the  ages  of  the  human  race — Nature 
will  find  room  for  both  the  philosophical  experimenter 
and  the  mathematician.  Faraday  entered  his  protest 
against  the  foregoing  statement  by  labelling  his  investiga- 
tions '  Experimental  Eesearches  in  Electricity.'  They 
were  completed  in  1854,  and  three  volumes  of  them  have 
been  published.  For  the  sake  of  reference,  he  numbered 
every  paragraph,  the  last  number  being  3362.  In  1859 
he  collected  and  published  a  fourth  volume  of  papers,  under 
the  title,  '  Experimental  Kesearches  in  Chemistry  and 
Physics.'  Thus  the  apostle  of  experiment  illustrated  its 
power,  and  magnified  his  office. 

The  second  volume  of  the  Eesearches  embraces  memoirs 
on  the  Electricity  of  the  G-ymnotus ;  on  the  Source  of 
Power  in  the  Voltaic  Pile ;  on  the  Electricity  evolved  by 
the  Friction  of  Water  and  Steam,  in  which  the  phenomena 
and  principles  of  Sir  William  Armstrong's  Hydro-electric 
machine  are  described  and  developed ;  a  paper  on  Mag- 
netic Rotations,  and  Faraday's  letters  in  relation  to  the 
controversy  it  aroused.  The  contribution  of  most  per- 
manent value  here,  is  that  on  the  Source  of  Power  in  the 
Voltaic  Pile.  By  it  the  Contact  Theory,  pure  and  simple, 
was  totally  overthrown,  and  the  necessity  of  chemical  action 
on  the  maintenance  of  the  current  demonstrated. 


FARADAY.  259 

The  third  volume  of  the  Eesearches  opens  with  a 
memoir  entitled  '  The  Magnetisation  of  Light,  and  the 
Illumination  of  Magnetic  Lines  of  Force.'  It  is  difficult 
even  now  to  affix  a  definite  meaning  to  this  title  ;  but  the 
discovery  of  the  rotation  of  the  plane  of  polarisation,  which 
it  announced,  seems  pregnant  with  great  results.  The 
writings  of  William  Thomson  on  the  theoretic  aspects  of 
the  discovery;  the  excellent  electro-dynamic  measure- 
ments of  Wilhelm  Weber,  which  are  models  of  experi- 
mental completeness  and  skill ;  Weber's  labours  in  con- 
junction with  his  lamented  friend  Kohlrausch — above  all, 
the  researches  of  Clerk  Maxwell  on  the  Electro-magnetic 
Theory  of  Light — point  to  that  wonderful  and  mysterious 
medium,  which  is  the  vehicle  of  light  and  radiant  heat,  as 
the  probable  basis  also  of  magnetic  and  electric  phenomena. 
The  hope  of  such  a  connection  was  first  raised  by  the 
discovery  here  referred  to.1  Faraday  himself  seemed  to 
cling  with  particular  affection  to  this  discovery.  He  felt 
that  there  was  more  in  it  than  he  was  able  to  unfold.  He 
predicted  that  it  would  grow  in  meaning  with  the  growth 
of  science.  This  it  has  done ;  this  it  is  doing  now.  Its 
right  interpretation  will  probably  mark  an  epoch  in  scien- 
tific history. 

Kapidly  following  it  is  the  discovery  of  Diamagnetism, 
or  the  Eepulsion  of  Matter  by  a  magnet.  Brugmans  had 
shown  that  bismuth  repelled  a  magnetic  needle.  Here  he 
stopped.  Le  Bailliff  proved  that  antimony  did  the  same. 

1  A  letter  addressed  to  me  by  Professor  Weber  on  March  18  last 
contains  the  following  reference  to  the  connection  here  mentioned :  '  Die 
Hoffnung  einer  solchen  Combination  ist  durch  Faraday's  Entdeekung  der 
Drehung  der  Polarisationsebene  durch  magnetische  Directionskraft  zuerst, 
und  sodann  durch  die  Uebereinstimmung  derjenigen  Geschwindigkeit, 
welche  das  Verhaltniss  der  electro-dynamischen  Einheit  zur  electro-sta- 
tischen  ausdriickt,  mit  der  Geschwindigkeit  des  Lichts  angeregt  worden  ; 
und  niir  scheint  von  alien  Versuchen,  welche  zur  Verwirklichung  dieser 
Hoffnung  gemacht  worden  sind,  das  von  Herrn  Maxwell  gemachte  am 
erfol  greichst  en .' 


'260  FRAGMENTS   OF   SCIENCE. 

Here  he  stopped.  Seebeck,  Becquerel,  and  others,  also 
touched  the  discovery.  These  fragmentary  gleams  excited 
a  momentary  curiosity,  and  \vere  almost  forgotten,  when 
Faraday,  independently,  alighted  on  the  same  facts  ;  and, 
instead  of  stopping,  made  them  the  inlets  to  a  new  and 
vast  region  of  research.  The  value  of  a  discovery  is  to  be 
measured  by  the  intellectual  action  it  calls  forth  ;  and  it 
was  Faraday's  good  fortune  to  strike  such  lodes  of  scien- 
tific truth  as  give  occupation  to  some  of  the  best  intellects 
of  our  age. 

The  salient  quality  of  Faraday's  scientific  character 
reveals  itself  from  beginning  to  end  of  these  volumes :  a 
union  of  ardour  and  patience — the  one  prompting  the 
attack,  the  other  holding  him  on  to  it,  till  defeat  was  final 
or  victory  assured.  Certainty  in  one  sense  or  the  other 
was  necessary  to  his  peace  of  mind.  The  right  method 
of  investigation  is  perhaps  incommunicable ;  it  depends 
on  the  individual  rather  than  on  the  system,  and  the 
mark  is  missed  when  Faraday's  researches  are  pointed  to 
as  merely  illustrative  of  the  power  of  the  inductive  philo- 
sophy. The  brain  may  be  filled  with  that  philosophy ; 
but  without  the  energy  and  insight  which  this  man  pos- 
sessed, and  which  with  him  were  personal  and  distinctive, 
we  should  never  rise  to  the  level  of  his  achievements. 
His  power  is  that  of  individual  genius,  rather  than  of 
philosophic  method ;  the  energy  of  a  strong  soul  express- 
ing itself  after  its  own  fashion,  and  acknowledging  no 
mediator  between  it  and  Nature. 

The  second  volume  of  the  '  Life  and  Letters,'  like  the 
first,  is  a  historic  treasury  as  regards  Faraday's  work  and 
character,  and  his  scientific  and  social  relations.  It 
contains  letters  from  Humboldt,  Herschel,  Hachette,  De 
la  Rive,  Dumas,  Liebig,  Melloni,  Becquerel,  Oersted, 
Pliicker,  Du  Bois  Eeymond,  Lord  Melbourne,  Prince 
Louis  Napoleon,  and  many  other  distinguished  men.  I 


FAKADAY.  261 

notice  with  particular  pleasure  a  letter  from  Sir  John 
Herschel,  in  reply  to  a  sealed  packet  addressed  to  him  by 
Faraday,  but  which  he  had  permission  to  open  if  he 
pleased.  The  packet  referred  to  one  of  the  many  unful- 
filled hopes  which  spring  up  in  the  mind  of  fertile  investi- 
gators : — 

'  Go  on  and  prosper,  "  from  strength  to  strength,"  like 
a  victor  marching  with  assured  step  to  further  conquests ; 
and  be  certain  that  no  voice  will  join  more  heartily  in  the 
peans  that  already  begin  to  rise,  and  will  speedily  swell 
into  a  shout  of  triumph,  astounding  even  to  yourself,  than 
thatofJ.F.W.  Herschel.' 

Faraday's  behaviour  to  Melloni  in  1835  merits  a  word 
of  notice.  The  young  man  was  a  political  exile  in  Paris. 
He  had  newly  fashioned  and  applied  the  thermo-electric 
pile,  and  had  obtained  with  it  results  of  the  greatest 
importance.  But  they  were  not  appreciated.  With  the 
sickness  of  disappointed  hope  Melloni  waited  for  the 
report  of  the  Commissioners,  appointed  by  the  Academy 
of  Sciences  to  examine  his  labours.  At  length  he  published 
his  researches  in  the  *  Annales  de  Chimie.'  They  thus 
fell  into  the  hands  of  Faraday,  who,  discerning  at  once 
their  extraordinary  merit,  obtained  for  their  author  the 
Kumford  Medal  of  the  Eoyal  Society.  A  sum  of  money 
always  accompanies  this  medal ;  and  the  pecuniary  help 
was,  at  this  time,  even  more  essential  than  the  mark  of 
honour  to  the  young  refugee.  Melloni's  gratitude  was 
boundless  : — 

'  Et  vous,  monsieur,'  he  writes  to  Faraday,  '  qui  appar- 
tenez  a  line  societe  a  laquelle  je  n'avais  rien  offert,  vous 
qui  me  connaissiez  a  peine  de  nom ;  vous  n'avez  pas 
demande  si  j'avais  des  ennemis  faibles  ou  puissants,  ni 
calcule  quel  en  etait  le  nombre ;  mais  vous  avez  parle 
pour  I'oppiime  etranger,  pour  celui  qui  n'avait  pas  le 
moindre  droit  a  tant  de  bienveillance,  et  vos  paroles  ont 


262  FRAGMENTS   OF   SCIENCE. 

ete  accueillies  favorablement  par  des  collogues  conscien- 
cieux  I  Je  reconnais  bien  la  des  hommes  dignes  de  leur 
noble  mission,  les  veritables  representants  de  la  science 
d'un  pays  libre  et  genereux.' 

Within  the  prescribed  limits  of  this  article  it  would  be 
impossible  to  give  even  the  slenderest  summary  of  Fara- 
day's correspondence,  or  to  carve  from  it  more  than  the 
merest  fragments  of  his  character.  His  letters,  written  to 
Lord  Melbourne  and  others  in  1836,  regarding  his  pension, 
illustrate  his  uncompromising  independence.  The  Prime 
Minister  had  offended  him,  but  assuredly  the  apology 
demanded  and  given  was  complete.  I  think  it  certain 
that,  notwithstanding  the  very  fidl  account  of  this  transac- 
tion given  by  Dr.  Bence  Jones,  motives  and  influences 
were  at  work  which  even  now  are  not  entirely  revealed. 
The  minister  was  bitterly  attacked,  but  he  bore  the 
censure  of  the  press  with  great  dignity.  Faraday,  while 
he  disavowed  having  either  directly  or  indirectly  furnished 
the  matter  of  those  attacks,  did  not  publicly  exonerate 
his  lordship.  The  Hon.  Caroline  Fox  had  proved  her- 
self Faraday's  ardent  friend,  and  it  was  she  who  had 
healed  the  breach  between  the  philosopher  and  the 
minister.  She  manifestly  thought  that  Faraday  ought  to 
have  come  forward  in  Lord  Melbourne's  defence,  and 
there  is  a  flavour  of  resentment  in  one  of  her  letters  to 
him  on  the  subject.  No  doubt  Faraday  had  good  grounds 
for  his  reticence,  but  they  are  to  me  unknown. 

In  1841  his  health  broke  down  utterly,  and  he  went 
to  Switzerland  with  his  wife  and  brother-in-law.  His 
bodily  vigour  soon  revived,  and  he  accomplished  feats  of 
walking  respectable  even  for  a  trained  mountaineer.  The 
published  extracts  from  his  Swiss  journal  contain  many 
beautiful  and  touching  allusions.  Amid  references  to  the 
tints  of  the  Jungfrau,  the  blue  rifts  of  the  glaciers,  and 
the  noble  Nieson  towering  over  the  Lake  of  Thun,  we 


FARADAY.  263 

come  upon  the  charming  little  scrap  which  I  have  else- 
where quoted  :  '  Clout-nail  making  goes  on  here  rather 
considerably,  and  is  a  very  neat  and  pretty  operation  to 
observe.  I  love  a  smith's  shop  and  anything  relating  to 
smithery.  My  father  was  a  smith.'  This  is  from  his 
journal ;  but  he  is  unconsciously  speaking  to  somebody — 
perhaps  to  the  world. 

His  descriptions  of  the  Staubbach,  Giessbach,  and  of 
the  scenic  effects  of  sky  and  mountain,  are  all  fine  and 
sympathetic.  But  amid  it  all,  and  in  reference  to  it  all, 
he  tells  his  sister  that  '  true  enjoyment  is  from  within,  not 
from  without.'  In  those  days  Agassiz  was  living  under  a 
slab  of  gneiss  on  the  glacier  of  the  Aar.  Faraday  met 
Forbes  at  the  Grimsel,  and  arranged  with  him  an  excur- 
sion to  the  '  Hotel  des  Neufchatelois  ; :  but  indisposition 
put  the  project  out. 

From  the  Fort  of  Ham,  in  1843,  Faraday  received  a 
letter  addressed  to  him  by  Prince  Louis  Napoleon  Bona- 
parte. He  read  this  letter  to  me  many  years  ago,  and 
the  desire,  shown  in  various  ways  by  the  French  Emperor, 
to  turn  modern  science  to  account,  has  often  reminded 
me  of  it  since.  At  the  age  of  thirty-five  the  prisoner  of 
Ham  speaks  of  'rendering  his  captivity  less  sad  by 
studying  the  great  discoveries  '  which  science  owes  to 
Faraday ;  and  he  asks  a  question  which  reveals  his  cast 
of  thought  at  the  time :  '  What  is  the  most  simple  com- 
bination to  give  to  a  voltaic  battery,  in  order  to  produce 
a  spark  capable  of  setting  fire  to  powder  under  water  01 
under  ground  ? '  Should  the  necessity  arise,  the  French 
Emperor  will  not  lack  at  the  outset  the  best  appliances  of 
modern  science ;  while  we,  I  fear,  shall  have  to  learn  the 
magnitude  of  the  resources  we  are  now  neglecting  amid 
the  pangs  of  actual  war.1 

1  The  '  science'  has  since  been  applied,  \rith  astonishing  effect,  by  those 
who  had  studied  it  far  more  thoroughly  than  the  Emperor  of  the  French. 


264  FRAGMENTS   OF  SCIENCE. 

One  turns  with  renewed  pleasure  to  Faraday's  letters 
to  his  wife,  published  in  the  second  volume.  Here  surely 
the  loving  essence  of  the  man  appears  more  distinctly 
than  anywhere  else.  From  the  house  of  Dr.  Percy,  in 
Birmingham,  he  writes  thus : — 

'Here — even  here — the  moment  I  leave  the  table,  I 
wish  I  were  with  you  IN  QUIET.     Oh,  what  happiness  is 
ours  !     My  runs  into  the  world  in  this  way  only  serve  to 
make  me  esteem  that  happiness  the  more.' 
And  again : 

'  We  have  been  to  a  grand  conversazione  in  the  town- 
hall,  and  I  have  now  returned  to  my  room  to  talk  with 
you,  as  the  pleasantest  and  happiest  thing  that  I  can  do. 
Nothing  rests  me  so  much  as  communion  with  you.  I 
feel  it  even  now  as  I  write,  and  catch  myself  saying  the 
words  aloud  as  I  write  them.' 

Take    this,    moreover,    as     indicative    of    his    love  for 
Nature : 

'  After  writing,  I  walk  out  in  the  evening  hand  in 
hand  with  my  dear  wife  to  enjoy  the  sunset ;  for  to  me 
who  love  scenery,  of  all  that  I  have  seen  or  can  see,  there 
is  none  surpasses  that  of  heaven.  A  glorious  sunset 
brings  with  it  a  t/iousand  thoughts  that  delight  me.' 

Of  the  numberless  lights  thrown  upon  him  by  the 
'  Life  and  Letters,'  some  fall  upon  his  religion.  In  a 
letter  to  a  lady,  he  describes  himself  as  belonging  to  *  a 
very  small  and  despised  sect  of  Christians,  known,  if 
known  at  all,  as  Sandemanians,  and  our  hope  is  founded 
on  the  faith  that  is  in  Christ.'  He  adds  :  '  I  do  not  think 
it  at  all  necessary  to  tie  the  study  of  the  natural  sciences 
and  religion  together,  and  in  my  intercourse  with  my 
fellow-creatures,  that  which  is  religious,  and  that  which 
is  philosophical,  have  ever  been  two  distinct  things.'  He 
saw  clearly  the  danger  of  quitting  his  moorings,  and  his 
science  acted  indirectly  as  the  safeguard  of  his  particular 


FAEADAT.  265 

faith.  For  his  investigations  so  filled  his  mind  as  to  leave 
no  room  for  sceptical  questionings,  thus  shielding  from  the 
assaults  of  philosophy  the  creed  of  his  youth.  His  religion 
was  constitutional  and  hereditary.  It  was  implied  in  the 
eddies  of  his  blood  and  in  the  tremors  of  his  brain ;  and, 
however  its  outward  and  visible  form  might  have  changed, 
Faraday  would  still  have  possessed  its  elemental  con- 
stituents— awe,  reverence,  truth,  and  love. 

It  is  worth  enquiring  how  so  profoundly  religious  a 
mind,  and  so  great  a  teacher,  would  be  likely  to  regard 
our  present  discussions  on  the  subject  of  education. 
Faraday  would  be  a  '  secularist '  were  he  now  alive.  He 
had  no  sympathy  with  those  who  contemn  knowledge 
unless  it  be  accompanied  by  dogma.  A  lecture  delivered 
before  the  City  Philosophical  Society  in  1818,  when  he 
was  twenty-six  years  of  age,  expresses  the  views  regarding 
education  which  he  entertained  to  the  end  of  his  life. 
1  First,  then,'  he  says,  '  all  theological  considerations  are 
banished  from  the  society,  and  of  course  from  my  remarks  ; 
and  whatever  I  may  say  has  no  reference  to  a  future  state, 
or  to  the  means  which  are  to  be  adopted  in  this  world 
in  anticipation  of  it.  Next,  I  have  no  intention  of 
substituting  anything  for  religion,  but  I  wish  to  take 
that  part  of  human  nature  which  is  independent  of  it. 
Morality,  philosophy,  commerce,  the  various  institutions 
and  habits  of  society,  are  independent  of  religion,  and  may 
exist  either  with  or  without  it.  They  are  always  the 
same,  and  can  dwell  alike  in  the  breasts  of  those  who, 
from  opinion,  are  entirely  opposed  in  the  set  of  principle? 
they  include  in  the  term  religion,  or  in  those  who  have 
none. 

'  To  discriminate  more  closely,  if  possible,  I  will  ob- 
serve that  we  have  no  right  to  judge  religious  opinions ; 
but  the  human  nature  of  this  evening  is  that  part  of  man 
which  we  have  a  right  to  judge.  And  I  think  it  will  be 


266  FRAGMENTS    OF   SCIENCE. 

found,  on  examination,  that  this  humanity — as  it  may 
perhaps  be  called — will  accord  with  what  I  have  before 
described  as  being  in  our  own  hands  so  improvable  and 
perfectible.' 

Among  my  old  papers  I  find  the  following  remarks  on 
one  of  my  earliest  dinners  with  Faraday :  *  At  two  o'clock 
he  came  down  for  me.  He,  his  niece,  and  myself,  formed 
the  party.  "  I  never  give  dinners,"  he  said.  "  I  don't 
know  how  to  give  dinners,  and  I  never  dine  out.  But  I 
should  not  like  my  friends  to  attribute  this  to  a  wrong 
cause.  I  act  thus  for  the  sake  of  securing  time  for  work, 
and  not  through  religious  motives,  as  some  imagine." 
He  said  grace.  I  am  almost  ashamed  to  call  his  prayer  a 
"  saying  of  grace."  In  the  language  of  Scripture,  it  might 
be  described  as  the  petition  of  a  son,  into  whose  heart 
God  had  sent  the  Spirit  of  His  Son,  and  who  with  abso- 
lute trust  asked  a  blessing  from  his  father.  We  dined  on 
roast  beef,  Yorkshire  pudding,  and  potatoes ;  drank 
sherry,  talked  of  research  and  its  requirements,  and  of 
his  habit  of  keeping  himself  free  from  the  distractions  of 
society.  He  was  bright  and  joyful — boylike,  in  fact, 
though  he  is  now  sixty-two.  His  work  excites  admiration, 
but  contact  with  him  warms  and  elevates  the  heart. 
Here,  surely,  is  a  strong  man.  I  love  strength ;  but  let 
me  not  forget  the  example  of  its  union  with  modesty, 
tenderness,  and  sweetness,  in  the  character  of  Faraday.' 

Faraday's  progress  in  discovery,  and  the  salient  points 
of  his  character,  are  well  brought  out  by  the  wise  choice 
of  letters  and  extracts  published  in  these  volumes.  I  will 
not  call  the  labours  of  the  biographer  final.  So  great  a 
character  will  challenge  reconstruction.  In  the  coming 
time  some  sympathetic  spirit,  with  the  requisite  strength, 
knowledge,  and  solvent  power,  will,  I  doubt  not,  render 
these  materials  plastic,  give  them  more  perfect  organic 
form,  and  send  through  them,  with  less  of  interruption, 


FARADAY.  207 

the  currents  of  Faraday's  life.  '  He  was  too  good  a  man,' 
writes  his  present  biographer,  '  for  me  to  estimate  rightly, 
and  too  great  a  philosopher  for  me  to  understand 
thoroughly.'  That  may  be:  but  the  reverent  affection  to 
which  we  owe  the  discovery,  selection,  and  arrangement 
of  the  materials  here  placed  before  us,  is  probably  a  surer 
guide  than  mere  literary  skill.  The  task  of  the  artist 
who  may  wish  in  future  times  to  reproduce  the  real 
though  unobtrusive  grandeur,  the  purity,  beauty,  and 
childlike  simplicity  of  him  whom  we  have  lost,  will  find 
his  chief  treasury  already  provided  for  him  by  Dr.  Bence 
Jones's  labour  of  love. 


14 


2«8  FRAGMENTS   OP  SCIENCE. 


IX. 

THE  COPLEY  MEDALIST  OF  1870. 

npHIETY  years  ago  Electro- magnetism  was  looked  to  as 
JL  a  motive  power,  which  might  possibly  compete  with 
steam.  In  centres  of  industry,  such  as  Manchester,  at- 
tempts to  investigate  and  apply  this  power  were  numerous. 
This  is  shown  by  the  scientific  literature  of  the  time. 
Among  others  Mr.  James  Prescot  Joule,  a  resident  of  Man- 
chester, took  up  the  subject,  and,  in  a  series  of  papers  pub- 
lished in  Sturgeon's  '  Annals  of  Electricity'  between  1839 
and  1841,  described  various  attempts  at  the  construction 
and  perfection  of  electro-magnetic  engines.  The  spirit  in 
which  Mr.  Joule  pursued  these  enquiries  is  revealed  in  the 
following  extract  :  '  I  am  particularly  anxious,'  he  says, 
4  to  communicate  any  new  arrangement  in  order,  if  possi- 
ble, to  forestall  the  monopolising  designs  of  those  who 
seem  to  regard  this  most  interesting  subject  merely  in  the 
light  of  pecuniary  speculation.'  He  was  naturally  led  to 
investigate  the  laws  of  electro-magnetic  attractions, 
and  in  1840  he  announced  the  important  principle  that 
the  attractive  force  exerted  by  two  electro-magnets,  or  by 
an  electro-magnet  and  a  mass  of  annealed  iron,  is  directly 
proportional  to  the  square  of  the  strength  of  the  magnet- 
ising current;  while  the  attraction  exerted  between  an 
electro-magnet  and  the  pole  of  a  permanent  steel  magnet, 
varies  simply  as  the  strength  of  the  current.  These 
investigations  were  conducted  independently  of,  though  a 


THE   COPLEY  MEDALIST   OF   1870.  269 

little  subsequently  to,  the  celebrated  enquiries  of  Henry, 
Jacobi,  and  Lenz  and  Jacobi,  on  the  same  subject. 

On  December  17,  1840,  Mr.  Joule  communicated  to 
the  Royal  Society  a  paper  on  the  production  of  heat 
by  Voltaic  electricity.  In  it  he  announced  the  law  that 
the  calorific  effects  of  equal  quantities  of  transmitted 
electricity  are  proportional  to  the  resistance  overcome 
by  the  current,  whatever  may  be  the  length,  thickness, 
shape,  or  character  of  the  metal  which  closes  the  cir- 
cuit; and  also  proportional  to  the  square  of  the  quantity 
of  transmitted  electricity.  This  is  a  law  of  primary 
importance.  In  another  paper,  presented  to,  but  de- 
clined by,  the  Royal  Society,  he  confirmed  this  law  by 
new  experiments,  and  materially  extended  it.  He  also 
executed  experiments  on  the  heat  consequent  on  the 
passage  of  Voltaic  electricity  through  electrolytes,  and 
found,  in  all  cases,  that  the  heat  evolved  by  the  proper 
action  of  any  Voltaic  current  is  proportional  to  the 
square  of  the  intensity  of  that  current,  multiplied  by  the 
resistance  to  conduction  which  it  experiences.  From 
this  law  he  deduced  a  number  of  conclusions  of  the 
highest  importance  to  electro-chemistry. 

It  was  during  these  enquiries,  which  are  marked 
throughout  by  rare  sagacity  and  originality,  that  the  great 
idea  of  establishing  quantitative  relations  between  Me- 
chanical Energy  and  Heat  arose  and  assumed  definite  form 
in  his  mind.  In  1843  Mr.  Joule  read  before  the  meeting 
of  the  British  Association  at  Cork  a  paper  '  On  the  Calorific 
Effects  of  Magneto-Electricity,  and  on  the  Mechanical 
Value  of  Heat.'  Even  at  the  present  day  this  memoir 
is  tough  reading,  and  at  the  time  it  was  written  it  must 
have  appeared  hopelessly  entangled.  This,  I  should 
think,  was  the  reason  why  Faraday  advised  Mr.  Joule 
not  to  submit  the  paper  to  the  Royal  Society.  But  its 
drift  and  results  are  summed  up  in  these  memorable 


270  FRAGMENTS   OP   SCIENCE. 

words  by  its  author,  written  some  time  subsequently :  '  In 
that  paper  it  was  demonstrated  experimentally,  that  the 
mechanical  power  exerted  in  turning  a  magneto-electric 
machine  is  converted  into  the  heat  evolved  by  the  passage 
of  the  currents  of  induction  through  its  coils ;  and,  on  the 
other  hand,  that  the  motive  power  of  the  electro-magnetic 
engine  is  obtained  at  the  expense  of  the  heat,  due  to  the 
chemical  .reaction  of  the  battery  by  which  it  is  worked.' l 
It  is  needless  to  dwell  upon  the  weight  and  importance  oi 
this  statement. 

Considering  the  imperfections  incidental  to  a  first 
determination,  it  is  not  surprising  that  the  '  mechanical 
values  of  heat,'  deduced  from  the  different  series  of  ex- 
periments published  in  1843,  varied  widely  from  each 
other.  The  lowest  limit  was  587,  and  the  highest  1,026 
foot-pounds,  for  1°  Fahr.  of  temperature. 

One  noteworthy  result  of  his  enquiries,  which  was 
pointed  out  at  the  time  by  Mr.  Joule,  had  reference 
to  the  exceedingly  small  fraction  of  the  heat  actually 
converted  into  useful  effect  in  the  steam-engine.  The 
thoughts  of  the  celebrated  Julius  Eobert  Mayer,  who 
was  then  engaged  in  Germany  upon  the  same  question, 
had  moved  independently  in  the  same  groove ;  but  to  his 
labours  due  reference  will  be  made  on  a  future  occa- 
sion.* In  the  memoir  now  referred  to,  Mr.  Joule  also 
announced  that  he  had  proved  heat  to  be  evolved  during 
the  passage  of  water  through  narrow  tubes ;  and  he 
deduced  from  these  experiments  an  equivalent  of  770 
foot-pounds,  a  figure  remarkably  near  the  one  now  ac- 
cepted. A  detached  statement  regarding  the  origin  and 
convertibility  of  animal  heat  strikingly  illustrates  the 
penetration  of  Mr.  Joule,  and  his  mastery  of  principles,  at 
the  period  now  referred  to.  A  friend  had  mentioned  to 

1  Phil.  Mag.  May,  1845.  2  See  the  next  Fragment 


THE   COPLEY    MEDALIST   OF    1870.  271 

him  Haller's  hypothesis,  that  animal  heat  might  arise 
from  the  friction  of  the  blood  in  the  veins  and  arteries. 
*  It  is  unquestionable,'  writes  Mr,  Joule,  *  that  heat  is 
produced  by  such  friction  ;  but  it  must  be  understood  that 
the  mechanical  force  expended  in  the  friction  is  a  part  of 
the  force  of  affinity  which  causes  the  venous  blood  to  unite 
with  oxygen,  so  that  the  whole  heat  of  the  system  must 
still  be  referred  to  the  chemical  changes.  But  if  the 
animal  were  engaged  in  turning  a  piece  of  machinery,  or 
in  ascending  a  mountain,  I  apprehend  that  in  proportion 
to  the  muscular  effort  put  forth  for  the  purpose,  a  dimi- 
nution of  the  heat  evolved  in  the  system  by  a  given 
chemical  action  would  be  experienced.'  The  italics  in 
this  memorable  passage,  written,  it  is  to  be  remembered, 
in  1843,  are  Mr.  Joule's  own. 

The  concluding  paragraph  of  this  British  Association 
paper  equally  illustrates  his  insight  and  precision,  regard- 
ing the  nature  of  chemical  and  latent  heat.  '  I  had,'  he 
writes,  '  endeavoured  to  prove  that  when  two  atoms 
combine  together,  the  heat  evolved  is  exactly  that  which 
would  have  been  evolved  by  the  electrical  current  due 
to  the  chemical  action  taking  place,  and  is  therefore  pro- 
portional to  the  intensity  of  the  chemical  force  causing 
the  atoms  to  combine.  I  now  venture  to  state  more 
explicitly,  that  it  is  not  precisely  the  attraction  of  affinity, 
but  rather  the  mechanical  force  expended  by  the  atoms  in 
falling  towards  one  another,  which  determines  the  in- 
tensity of  the  current,  and,  consequently,  the  quantity  of 
heat  evolved ;  so  that  we  have  a  simple  hypothesis  by 
which  we  may  explain  why  heat  is  evolved  so  freely  in 
the  combination  of  gases,  and  by  which  indeed  we  may 
account  "  latent  heat "  as  a  mechanical  power,  prepared 
for  action,  as  a  watch-spring  is  when  wound  up.  Suppose, 
for  the  sake  of  illustration,  that  8  Ibs.  of  oxygen  and 
1  Ib.  of  hydrogen  were  presented  to  one  another  in  the 


272  FRAGMENTS    OF   SCIENCE. 

gaseous  state,  and  then  exploded  ;  the  heat  evolved  would 
be  about  1°  Fahr.  in  60,000  Ibs.  of  water,  indicating  a  me- 
chanical force,  expended  in  the  combination,  equal  to  a 
weight  of  about  50,000,000  Ibs.  raised  to  the  height  of  one 
foot.  Now  if  the  oxygen  and  hydrogen  could  be  presented 
to  each  other  in  a  liquid  state,  the  heat  of  combination 
would  be  less  than  before,  because  the  atoms  in  com- 
bining would  fall  through  less  space.'  No  words  of  mine 
axe  needed  to  point  out  the  commanding  grasp  of  mole- 
cular physics,  in  their  relation  to  the  mechanical  theory  of 
heat,  implied  by  this  statement. 

Perfectly  assured  of  the  importance  of  the  principle 
which  his  experiments  aimed  at  establishing,  Mr.  Joule 
did  not  rest  content  with  results  presenting  such  discre- 
pancies as  those  above  referred  to.  He  resorted  in  1844 
to  entirely  new  methods,  and  made  elaborate  experiments 
on  the  thermal  changes  produced  in  air  during  its  expan- 
sion :  firstly,  against  a  pressure,  and  therefore  performing 
work  ;  secondly,  against  no  pressure,  and  therefore  per- 
forming no  work.  He  thus  established  anew  the  relation 
between  the  heat  consumed  and  the  work  done.  From 
five  different  series  of  experiments  he  deduced  five 
different  mechanical  equivalents  ;  the  agreement  between 
them  being  far  greater  than  that  attained  in  his  first 
experiments.  The  mean  of  them  was  802  foot-pounds. 
From  experiments  with  water  agitated  by  a  paddle-wheel, 
he  deduced,  in  1845,  an  equivalent  of  890  foot-pounds. 
In  1847  he  again  operated  upon  water  and  sperm-oil, 
agitated  them  by  a  paddle-wheel,  determined  their  eleva- 
tion of  temperature,  and  the  mechanical  power  which 
produced  it.  From  the  one  he  derived  an  equivalent  of 
781'5  foot-pounds;  from  the  other  an  equivalent  of  782*1 
foot-pounds.  The  mean. of  these  two  very  close  deter- 
minations is  781*8  foot-pounds. 

At  this  time  the  labours  of  the  previous  ten  years  had 


THE   COPLEY  MEDALIST   OF   1870.  278 

made  Mr.  Joule  completely  master  of  the  conditions  es- 
sential to  accuracy  and  success.  Bringing  his  ripened 
experience  to  bear  upon  the  subject,  he  executed  in  1849 
a  series  of  40  experiments  on  the  friction  of  water,  50 
experiments  on  the  friction  of  mercury,  and  20  experi- 
ments on  the  friction  of  plates  of  cast-iron.  He  deduced 
from  these  experiments  our  present  mechanical  equivalent 
sf  heat,  justly  recognised  all  over  the  world  as 'Joule's 
equivalent.' 

There  are  labours  so  great  and  so  pregnant  in  conse- 
quences, that  they  are  most  highly  praised  when  they  are 
most  simply  stated.  Such  are  the  labours  of  Mr.  Joule. 
They  constitute  the  experimental  foundation  of  a  principle 
of  incalculable  moment,  not  only  to  the  practice,  but  still 
more  to  the  philosophy  of  Science.  Since  the  days  of 
Newton,  nothing  more  important  than  the  theory,  of 
which  Mr.  Joule  is  the  experimental  demonstrator,  has 
been  enunciated. 

I  have  omitted  all  reference  to  the  numerous  minor 
papers  with  which  Mr.  Joule  has  enriched  scientific  litera- 
ture. Nor  have  I  alluded  to  the  important  investigations 
which  he  has  conducted  jointly  with  Sir  William  Thom- 
son. But  sufficient,  I  think,  has  been  here  said  to  show 
that,  in  conferring  upon  Mr.  Joule  the  highest  honour  of 
the  Koyal  Society,  the  Council  paid  to  genius  not  only  a 
well-won  tribute,  but  one  which  had  been  fairly  earned 
twenty  years  previously. 


274  FRAGMENTS   OF   SCIENCE. 


X. 

THE  COPLEY  MEDALIST  OF  1871. 

DR.  JULIUS  ROBERT  MAYER  was  educated  for  the 
medical  profession.  In  the  summer  of  1840,  as  he 
himself  informs  us,  he  was  at  Java,  and  there  observed  that 
the  venous  blood  of  some  of  his  patients  had  a  singularly 
bright  red  colour.  The  observation  riveted  his  attention; 
he  reasoned  upon  it,  and  came  to  the  conclusion  that  the 
brightness  of  the  colour  was  due  to  the  fact  that  a  less 
amount  of  oxidation  sufficed  to  keep  up  the  temperature 
of  the  body  in  a  hot  climate  than  in  a  cold  one.  The 
darkness  of  the  venous  blood  he  regarded  as  the  visible 
sign  of  the  energy  of  the  oxidation. 

It  would  be  trivial  to  remark  that  accidents  such  as 
this,  appealing  to  minds  prepared  for  them,  have  often 
led  to  great  discoveries.  Mayer's  attention  was  thereby 
drawn  to  the  whole  question  of  animal  heat.  Lavoisier 
had  ascribed  this  heat  to  the  oxidation  of  the  food.  '  One 
great  principle,'  says  Mayer,  '  of  the  physiological  theory 
of  combustion,  is  that  under  all  circumstances  the  same 
amount  of  fuel  yields,  by  its  perfect  combustion,  the  same 
amount  of  heat ;  that  this  law  holds  good  even  for  vital 
processes  ;  and  that  hence  the  living  body,  notwithstand- 
ing all  its  enigmas  and  wonders,  is  incompetent  to  generate 
heat  out  of  nothing.' 

But  beyond  the  power  of  generating  internal  heat,  the 
animal  organism  can  also  generate  heat  outside  of  itself. 


THE   COPLEY   MEDALIST   OF   1871.  275 

A  blacksmith,  for  example,  by  hammering  can  heat  a  nail, 
and  a  savage  by  friction  can  warm  wood  to  its  point  of 
ignition.  Now,  unless  we  give  up  the  physiological  axiom 
that  the  living  body  cannot  create  heat  out  of  nothing, 
'  we  are  driven,'  says  Mayer,  *  to  the  conclusion  that  it  is 
the  total  heat  generated  within  and  without  that  is  to  be 
regarded  as  the  true  calorific  effect  of  the  matter  oxidised 
in  the  body.' 

From  this,  again,  he  inferred  that  the  heat  generated 
externally  must  stand  in  a  fixed  relation  to  the  work 
expended  in  its  production.  For,  supposing  the  organic 
processes  to  remain  the  same ;  if  it  were  possible,  by  the 
mere  alteration  of  the  apparatus,  to  generate  different 
amounts  of  heat  by  the  same  amount  of  work,  it  would 
follow  that  the  oxidation  of  the  same  amount  of  material 
would  sometimes  yield  a  less,  sometimes  a  greater, 
quantity  of  heat.  '  Hence,'  says  Mayer,  '  that  a  fixed 
relation  subsists  between  heat  and  work,  is  a  postulate  of 
the  physiological  theory  of  combustion.' 

This  is  the  simple  and  natural  account,  given  subse- 
quently by  Mayer  himself,  of  the  course  of  thought  started 
by  his  observation  in  Java.  But  the  conviction  once 
formed,  that  an  unalterable  relation  subsists  between  work 
and  heat,  it  was  inevitable  that  Mayer  should  seek  to 
express  it  numerically.  It  was  also  inevitable  that  a  mind 
like  his,  having  raised  itself  to  clearness  on  this  important 
point,  should  push  forward  to  consider  the  relationship  of 
natural  forces  generally.  At  the  beginning  of  1842  his 
work  had  made  considerable  progress ;  but  he  had  become 
physician  to  the  town  of  Heilbronn,  and  the  duties  of  his 
profession  limited  the  time  which  he  could  devote  to 
purely  scientific  enquiry.  He  thought  it  wise,  therefore, 
to  secure  himself  against  accident,  and  in  the  spring  of 
1842  wrote  to  Liebig,  asking  him  to  publish  in .  his 
Annalen '  a  brief  preliminary  notice  of  the  work  then 


276  FRAGMENTS    OF   SCIENCE. 

accomplished.  Liebig  did  so,  and  Dr.  Mayer's  first 
paper  is  contained  in  the  May  number  of  the  *  Annalen ' 
for  1842. 

Mayer  had  reached  his  conclusions  by  reflecting  on  the 
complex  processes  of  the  living  body ;  but  his  first  step 
in  public  was  to  state  definitely  the  physical  principles  on 
which  his  physiological  deductions  were  to  rest.  He 
begins,  therefore,  with  the  forces  of  inorganic  nature. 
He  finds  in  the  universe  two  systems  of  causes  which  are 
not  mutually  convertible  ; — the  different  kinds  of  matter 
and  the  different  forms  of  force.  The  first  quality  of  both 
he  affirms  to  be  indestructibility.  A  force  cannot  become 
nothing,  nor  can  it  arise  from  nothing.  Forces  are  con- 
vertible but  not  destructible.  In  the  terminology  of  his 
time,  he  then  gives  clear  expression  to  the  ideas  of  poten- 
tial and  dynamic  energy,  illustrating  his  point  by  a  weight 
resting  upon  the  earth,  suspended  at  a  height  above  the 
earth,  and  actually  falling  to  the  earth.  He  next  fixes 
his  attention  on  cases  where  motion  is  apparently  des- 
troyed, without  producing  other  motion  ;  on  the  shock  of 
inelastic  bodies,  for  example.  Under  what  form  does  the 
vanished  motion  maintain  itself?  Experiment  alone,  says 
Mayer,  can  help  us  here.  He  warms  water  by  stirring 
it ;  he  refers  to  the  force  expended  in  overcoming  friction. 
Motion  in  both  cases  disappears;  but  heat  is  generated, 
and  the  quantity  generated  is  the  equivalent  of  the  motion 
destroyed.  '  Our  locomotives,'  he  observes  with  extra- 
ordinary sagacity,  'may  be  compared  to  distilling  ap- 
paratus :  the  heat  beneath  the  boiler  passes  into  the 
motion  of  the  train,  and  is  again  deposited  as  heat  in  the 
axles  and  wheels.' 

A  numerical  solution  of  the  relation  between  heat  and 
work  was  what  Mayer  aimed  at,  and  towards  the  end  of 
his  first  paper  he  makes  the  attempt.  It  was  known  that 
a  definite  amount  of  air,  in  rising  one  degree  in  tempera- 


THE   COPLEY   MEDALIST   OF   1871.  277 

ture,  can  take  up  two  different  amounts  of  heat.  If  its 
volume  be  kept  constant,  it  takes  up  one  amount :  if  its 
pressure  be  kept  constant  it  takes  up  a  different  amount. 
These  two  amounts  are  called  the  specific  heat  under  con- 
stant volume  and  under  constant  pressure.  The  ratio  of  the 
first  to  the  second  is  as  1  :  1-421.  No  man,  to  my  know- 
ledge, prior  to  Dr.  Mayer,  penetrated  the  significance  of 
these  two  numbers.  He  first  saw  that  the  excess  0-421 
was  not,  as  then  universally  supposed,  heat  actually 
lodged  in  the  gas,  but  heat  which  had  been  actually  con- 
sumed by  the  gas  in  expanding  against  pressure.  The 
amount  of  work  here  performed  was  accurately  known, 
the  amount  of  heat  consumed  was  also  accurately  known, 
tnd  from  these  data  Mayer  determined  the  mechanical 
equivalent  of  heat.  Even  in  this  first  paper  he  is  able  to 
direct  attention  to  the  enormous  discrepancy  between  the 
theoretic  power  of  the  fuel  consumed  in  steam-engines,  and 
their  useful  effect. 

Though  this  paper  contains  but  the  germ  of  his 
further  labours,  I  think  it  may  be  safely  assumed  that,  as 
regards  the  mechanical  theory  of  heat,  this  obscure  Heil- 
bronn  physician,  in  the  year  1842,  was  in  advance  of  all 
the  scientific  men  of  the  time. 

Having,  by  the  publication  of  this  paper,  secured  him- 
self against  what  he  calls  '  Eventualitaten,'  he  devoted 
every  hour  of  his  spare  time  to  his  studies,  and  in  1845 
published  a  memoir  which  far  transcends  his  first  one  in 
weight  and  fulness,  and,  indeed,  marks  an  epoch  in  the 
history  of  science.  The  title  of  Mayer's  first  paper  was, 
*  Remarks  on  the  Forces  of  Inorganic  Nature.'  The  title 
of  his  second  great  essay  was,  '  Organic  Motion  in  its 
Connection  with  Nutrition.'  In  it  he  expands  and  illus- 
trates the  physical  principles  laid  down  in  his  first  brief 
paper.  He  goes  fully  through  the  calculation  of  the 
mechanical  equivalent  of  heat.  He  calculates  the  per- 


278  FKAGMENTS   OP   SCIENCE. 

formances  of  steam-engines,  and  finds  that  lOOlbs.  of  coal, 
in  a  good  working  engine,  produce  only  the  same  amount 
of  heat  as  95  Ibs.  in  an  un working  one ;  the  5  Ibs.  dis- 
appearing having  been  converted  into  work.  He  deter- 
mines the  useful  effect  of  gunpowder,  and  finds  nine  per 
cent,  of  the  force  of  the  consumed  charcoal  invested  on 
the  moving  ball.  He  records  observations  on  the  heat 
generated  in  water  agitated  by  the  pul ping-engine  of  a 
paper  manufactory,  and  calculates  the  equivalent  of  that 
heat  in  horse-power.  He  compares  chemical  combination 
with  mechanical  combination — the  union  of  atoms  with 
the  union  of  falling  bodies  with  the  earth.  He  calculates 
the  velocity  with  which  a  body  starting  at  an  infinite 
distance  would  strike  the  earth's  surface,  and  finds  that 
the  heat  generated  by  its  collision  would  raise  an  equal 
weight  of  water  17,356°  C.  in  temperature.  He  then 
determines  the  thermal  effect  which  would  be  produced 
by  the  earth  itself  falling  into  the  sun.  So  that  here,  in 
1845,  we  have  the  germ  of  that  meteoric  theory  of  the 
sun's  heat  which  Mayer  developed  with  such  extraordinary 
ability  three  years  afterwards.  He  also  points  to  the 
almost  exclusive  efficacy  of  the  sun's  heat  in  producing 
mechanical  motions  upon  the  earth,  winding  up  with  the 
profound  remark,  that  the  heat  developed  by  friction  in 
the  wheels  of  our  wind  and  water  mills  comes  from  the 
sun  in  the  form  of  vibratory  motion ;  while  the  heat  pro- 
duced by  mills  driven  by  tidal  action  is  generated  at  the 
expense  of  the  earth's  axial  rotation. 

Having  thus,  with  firm  step,  passed  through  the  powers 
of  inorganic  nature,  his  next  object  is  to  bring  his  prin- 
ciples to  bear  upon  the  phenomena  of  vegetable  and 
animal  life.  Wood  and  coal  can  burn ;  whence  come 
their  heat,  and  the  work  producible  by  that  heat  ?  From 
the  immeasurable  reservoir  of  the  sun.  Nature  has 
proposed  to  herself  the  task  of  storing  up  the  light  which 


THE   COPLEY   MEDALIST   OF    1871.  279 

streams  earthward  from  the  sun,  and  of  casting  into  a 
permanent  form  the  most  fugitive  of  all  powers.  To  this 
end  she  has  overspread  the  earth  with  organisms  which, 
while  living,  take  in  the  solar  light,  and  by  its  consump- 
tion generate  forces  of  another  kind.  These  organisms 
are  plants.  The  vegetable  world,  indeed,  constitutes  the 
instrument  whereby  the  wave-motion  of  the  sun  is  changed 
into  the  rigid  form  of  chemical  tension,  and  thus  prepared 
for  future  use.  With  this  prevision,  as  shall  subsequently 
be  shown,  the  existence  of  the  human  race  itself  is  insepar- 
ably connected.  It  is  to  be  observed  that  Mayer's  utter- 
ances are  far  from  being  anticipated  by  vague  statements 
regarding  the  '  stimulus '  of  light,  or  regarding  coal  as 
'  bottled  sunlight.'  He  first  saw  the  full  meaning  of  De 
Saussure's  observation  of  the  reducing  power  of  the  solar 
rays,  and  gave  that  observation  its  proper  place  in  the 
doctrine  of  conservation.  In  the  leaves  of  a  tree,  the 
carbon  and  oxygen  of  carbonic  acid,  and  the  hydrogen  and 
oxygen  of  water,  are  forced  asunder  at  the  expense  of  the 
sun,  and  the  amount  of  power  thus  sacrificed  is  accurately 
restored  by  the  combustion  of  the  tree.  The  heat  and 
work  potential  in  our  coal  strata  are  so  much  strength 
withdrawn  from  the  sun  of  former  ages.  Mayer  lays  the 
axe  to  the  root  of  many  notions  regarding  '  vital  force ' 
which  were  prevalent  when  he  wrote.  With  the  plain 
fact  before  us  that  plants  cannot  perform  the  work  of 
reduction,  or  generate  chemical  tensions,  in  the  absence 
of  the  solar  rays,  it  is,  he  contends,  incredible  that  these 
tensions  should  be  caused  by  the  mystic  play  of  the  vital 
force.  Such  an  hypothesis  would  cut  off  all  investigation  ; 
it  would  land  us  in  a  chaos  of  unbridled  phantasy.  '  I 
count,'  he  says,  '  therefore,  upon  assent  when  I  state,  as  an 
axiomatic  truth,  that  during  vital  processes  the  conver- 
sion only,  and  never  the  creation  of  matter  or  force 
occurs.' 


280  FRAGMENTS    OF   SCIENCE. 

Having  cleared  his  way  through  the  vegetable  world, 
as  he  had  previously  done  through  inorganic  nature, 
Mayer  passes  on  to  the  other  organic  kingdom.  The 
physical  forces  collected  by  plants  become  the  property 
of  animals.  Animals  consume  vegetables,  and  cause 
them  to  reunite  with  the  atmospheric  oxygen.  Animal 
heat  is  thus  produced ;  and  not  only  animal  heat,  but 
animal  motion.  There  is  no  indistinctness  about  Mayer 
here  ;  he  grasps  his  subject  in  all  its  details,  and  reduces 
to  figures  the  concomitants  of  muscular  action.  A  bowler 
who  imparts  to  an  8-lb.  ball  a  velocity  of  30  feet,  con- 
sumes in  the  act  -fa  of  a  grain  of  carbon.  A  man 
weighing  150  Ibs.,  who  lifts  his  own  body  to  a  height  of 
8  feet,  consumes  in  the  act  1  grain  of  carbon.  In  climb- 
ing a  mountain  10,000  feet  high,  the  consumption  of  the 
same  man.  would  be  2  oz.  4  drs.  50  grs.  of  carbon. 
Boussingault  had  determined  experimentally  the  addition 
to  be  made  to  the  food  of  horses  when  actively  working, 
and  Liebig  had  determined  the  addition  to  be  made  in 
the  case  of  men.  Employing  the  mechanical  equivalent 
of  heat,  which  he  had  previously  calculated,  Mayer  proves 
the  additional  food  to  be  amply  sufficient  to  cover  the 
increased  oxidation. 

But  he  does  not  content  himself  with  showing,  in  a 
general  way,  that  the  human  body  burns  according  to 
definite  laws,  when  it  performs  mechanical  work.  He 
seeks  to  determine  the  particular  portion  of  the  body  con- 
sumed, and  in  doing  so  executes  some  noteworthy  calcula- 
tions. The  muscles  of  a  labourer  150  Ibs.  in  weight  weigh 
64  Ibs.;  when  perfectly  desiccated  they  fall  to  15  Ibs 
Were  the  oxidation  corresponding  to  that  labourer's  work 
exerted  on  the  muscles  alone,  they  would  be  utterly  con- 
sumed in  80  days.  The  heart  furnishes  a  still  more  striking 
example.  Were  the  oxidation  necessary  to  sustain  the 
heart's  action  exerted  upon  its  own  tissue,  it  would  be  utterly 


THE   COPLEY   MEDALIST   OF   1871.  281 

consumed  in  8  days.  And  if  we  confine  our  attention  to 
the  two  ventricles,  their  action  would  be  sufficient  to 
consume  the  associated  muscular  tissue  in  3^  days.  Here, 
in  his  own  words,  emphasised  in  his  own  way,  is  Mayer's 
pregnant  conclusion  from  these  calculations :  '  The  muscle 
is  only  the  apparatus  by  means  of  which  the  conversion  of 
the  force  is  effected ;  but  it  is  not  the  substance  consumed 
in  the  production  of  the  mechanical  effect.''  He  calls  the 
blood  '  the  oil  of  the  lamp  of  life  ; '  it  is  the  slow-burning 
fluid  whose  chemical  force,  in  the  furnace  of  the  capilla- 
ries, is  sacrificed  to  produce  animal  motion.  This  was 
Mayer's  conclusion  twenty-six  years  ago.  It  was  in 
complete  opposition  to  the  scientific  conclusions  of  his 
time ;  but  eminent  investigators  have  since  amply  veri- 
fied it. 

Thus,  in  baldest  outline,  I  have  sought  to  give  some 
notion  of  the  first  half  of  this  marvellous  essay.  The 
second  half  is  so  exclusively  physiological  that  I  do  not 
wish  to  meddle  with  it.  I  will  only  add  the  illustration 
employed  by  Mayer  to  explain  the  action  of  the  nerves 
upon  the  muscles.  As  an  engineer,  by  the  motion  of  his 
finger  in  opening  a  valve  or  loosing  a  detent,  can  liberate 
an  amount  of  mechanical  motion  almost  infinite  com- 
pared with  its  exciting  cause,  so  the  nerves,  acting  upon 
the  muscles,  can  unlock  an  amount  of  activity,  wholly 
out  of  proportion  to  the  work  done  by  the  nerves  them- 
selves. 

As  regards  these  questions  of  weightiest  import  to  the 
science  of  physiology,  Dr.  Mayer,  in  1845,  was  assuredly 
far  in  advance  of  all  living  men. 

Mayer  grasped  the  mechanical  theory  of  heat  with 
commanding  power,  illustrating  it  and  applying  it  in  the 
most  diverse  domains.  He  began,  as  we  have  seen,  with 
physical  principles ;  he  determined  the  numerical  rela- 
tion between  heat  and  work ;  he  revealed  the  source  of 


282  FKAGMENTS   OP   SCIENCE. 

the  energies  of  the  vegetable  world,  and  showed  the  rela- 
tionship of  the  heat  of  our  fires  to  solar  heat.  He  followed 
the  energies  which  were  potential  in  the  vegetable,  up  to 
their  local  exhaustion  in  the  animal.  But  in  1845  a  new 
thought  was  forced  upon  him  by  his  calculations.  He 
then,  for  the  first  time,  drew  attention  to  the  astounding 
amount  of  heat  generated  by  gravity  where  the  force 
has  sufficient  distance  to  act  through.  He  proved,  as  I 
have  before  stated,  the  heat  of  collision  of  a  body  falling 
from  an  infinite  distance  to  the  earth,  to  be  sufficient  to 
raise  the  temperature  of  a  quantity  of  water,  equal  to  the 
falling  body  in  weight,  1 7,356°  0.  He  also  found,  in  1845, 
that  the  gravitating  force  between  the  earth  and  sun  was 
competent  to  generate  an  amount  of  heat  equal  to  that 
obtainable  from  the  combustion  of  6,000  times  the  weight 
of  the  earth  of  solid  coal.  With  the  quickness  of  genius 
he  saw  that  we  had  here  a  power  sufficient  to  produce  the 
enormous  temperature  of  the  sun,  and  also  to  account  for 
the  primal  molten  condition  of  our  own  planet.  Mayer 
shows  the  utter  inadequacy  of  chemical  forces,  as  we  know 
them,  to  produce  or  maintain  the  solar  temperature.  He 
shows  that  were  the  sun  a  lump  of  coal  it  would  be 
utterly  consumed  in  5,000  years.  He  shows  the  diffi- 
culties attending  the  assumption  that  the  sun  is  a  cooling 
body ;  for,  supposing  it  to  possess  even  the  high  specific 
heat  of  water,  its  temperature  would  fall  15,000°  in  5,000 
years.  He  finally  concludes  that  the  light  and  heat  of 
the  sun  are  maintained  by  the  constant  impact  of  meteoric 
matter.  I  never  ventured  an  opinion  as  to  the  accuracy 
of  this  theory ;  that  is  a  question  which  may  still  have  to 
be  fought  out.  But  I  refer  to  it  as  an  illustration  of  the 
force  of  genius,  with  which  Mayer  followed  the  mechanical 
theory  of  heat  through  all  its  applications.  Whether  the 
meteoric  theory  be  a  matter  of  fact  or  not,  with  him 
abides  the  honour  of  proving  to  demonstration  that  the 


THE   COPLEY  MEDALIST   OF    1871.  283 

light  and  heat  of  suns  and  stars  may  be  originated  and 
maintained  by  the  collisions  of  cold  planetary  matter. 

It  is  the  man  who  with  the  scantiest  data  could  accom- 
plish all  this  in  six  short  years,  and  in  the  hours  snatched 
from  the  duties  of  an  arduous  profession,  that  the  Eoyal 
Society,  in  1871,  crowned  with  its  highest  honour.  Dr. 
Mayer  had  never  previously  received  any  mark  of  recog- 
nition from  the  Society. 

Comparing  this  brief  history  with  that  of  the  Copley 
Medalist  of  1870,  the  differentiating  influence  of  '  environ- 
ment,' on  two  minds  of  similar  natural  cast  and  endow- 
ment, comes  out  in  an  instructive  manner.  Withdrawn 
from  mechanical  appliances,  Mayer  fell  back  upon  reflec- 
tion, selecting  with  marvellous  sagacity,  from  existing 
physical  data,  the  single  result  on  which  eould  be  founded 
a  calculation  of  the  mechanical  equivalent  of  heat.  In 
the  midst  of  mechanical  appliances,  Joule  resorted  to  ex- 
periment, and  laid  the  broad  and  firm  foundation  which 
has  secured  for  the  mechanical  theory  the  acceptance  it 
now  enjoys.  A  great  portion  of  Joule's  time  was  occupied 
in  actual  manipulation ;  freed  from  this,  Mayer  had  time 
to  follow  the  theory  into  its  most  abtruse  and  impres- 
sive applications.  With  their  places  reversed,  however, 
Joule  might  have  become  Mayer,  and  Mayer  might  have 
become  Joule. 

It  does  not  lie  in  the  way  of  these  brief  articles  to 
enter  upon  the  great  developments  of  the  Dynamical 
Theory,  accomplished  since  Joule  and  Mayer  executed 
their  memorable  labcurs. 


284  FRAGMENTS    OF   SCIENCE. 


XI. 

ELEMENTARY  MAGNETISM. 

A  tECTTTRE  TO   SCHOOLMASTERS. 

WE  have  no  reason  to  believe  that  the  sheep  or  the 
dog,  or  indeed  any  of  the  lower  animals,  feel  an 
interest  in  the  laws  by  which  natural  phenomena  are  regu- 
lated. A  herd  may  be  terrified  by  a  thunder-storm  ;  birds 
may  go  to  roost,  and  cattle  return  to  their  stalls,  during  a 
solar  eclipse ;  but  neither  birds  nor  cattle,  as  far  as  we 
know,  ever  think  of  enquiring  into  the  causes  of  these 
things.  It  is  otherwise  with  man.  The  presence  of 
natural  objects,  the  occurrence  of  natural  events,  the 
varied  appearances  of  the  universe  in  which  he  dwells, 
penetrate  beyond  his  organs  of  sense,  and  appeal  to  an 
inner  power  of  which  the  senses  are  the  mere  instruments 
and  excitants.  No  fact  is  to  him  either  final  or  original. 
He  cannot  limit  himself  to  the  contemplation  of  it  alone, 
but  endeavours  to  ascertain  its  position  in  a  series  to  which 
the  constitution  of  his  mind  assures  him  it  must  belong. 
He  regards  all  that  he  witnesses  in  the  present  as  the 
efflux  and  sequence  of  something  that  has  gone  before, 
•and  as  the  source  of  a  system  of  events  which  is  to  follow. 
The  notion  of  spontaneity,  by  which  in  his  ruder  state  he 
accounted  for  natural  events,  is  abandoned  ;  the  idea  that 
nature  is  an  aggregate  of  independent  parts  also  disap- 
pears, as  the  connection  and  mutual  dependence  of  phy- 
sical powers  become  more  and  more  manifest :  until  he  is 
finally  led,  and  that  chiefly  by  the  science  of  which  I 


MAGNETISM.  286 

happen  this  evening  to  be  the  exponent,  to  regard  Nature 
as  an  organic  whole — as  a  body  each  of  whose  members 
sympathises  with  the  rest,  changing,  it  is  true,  from  age 
to  age,  but  without  one  real  break  of  continuity,  or  a  single 
interruption  of  the  fixed  relation  of  cause  and  effect. 

The  system  of  things  which  we  call  Nature  is,  how- 
ever, too  vast  and  various  to  be  studied  first-hand  by  any 
single  mind.  As  knowledge  extends  there  is  always  a 
tendency  to  subdivide  the  field  of  investigation.  Its 
various  parts  are  taken  up  by  different  individuals,  and 
thus  receive  a  greater  amount  of  attention  than  could 
possibly  be  bestowed  on  them  if  each  investigator  aimed 
at  the  mastery  of  the  whole.  East,  west,  north,  and  south, 
the  human  mind  pushes  its  conquests ;  but  the  centrifugal 
form  in  which  knowledge,  as  a  whole,  advances,  spreading 
ever  wider  on  all  sides,  is  due  in  reality  to  the  exertions 
of  individuals,  each  of  whom  directs  his  efforts,  more  or 
less,  along  a  single  line.  Accepting,  in  many  respects, 
his  culture  from  his  fellow-men — taking  it  from  spoken 
words  and  from  written  books,  in  some  one  direction,  the 
student  of  Nature  must  actually  touch  his  work.  He  may 
otherwise  be  a  distributor  of  knowledge,  but  not  a  creator, 
and  he  fails  to  attain  that  vitality  of  thought,  and  correct- 
ness of  judgment,  which  direct  and  habitual  contact  with 
natural  truth  can  alone  impart. 

One  large  department  of  the  system  of  Nature  which 
forms  the  chief  subject  of  my  own  studies,  and  to  which 
it  is  my  duty  to  call  your  attention  this  evening,  is  that 
of  physics,  or  natural  philosophy.  This  term  is  large 
enough  to  cover  the  study  of  Nature  generally,  but  it  is 
usually  restricted  to  a  department  which,  perhaps,  lies 
closer  to  our  perceptions  than  any  other.  It  deals  with 
the  phenomena  and  laws  of  light  and  heat — with  the 
phenomena  and  laws  of  magnetism  and  electricity — with 
those  of  sound — with  the  pressures  and  motions  of  liquids 


286  FRAGMENTS   OF   SCIENCE. 

and  gases,  whether  in  a  state  of  translation  or  of  undula- 
tion. The  science  of  mechanics  is  a  portion  of  natural 
philosophy,  though  at  present  so  large  as  to  need  the  ex- 
clusive attention  of  him  who  would  cultivate  it  pro- 
foundly. Astronomy  is  the  application  of  physics  to  the 
motions  of  the  heavenly  bodies,  the  vastness  of  the  field 
causing  it,  however,  to  he  regarded  as  a  department  in  it- 
self. In  chemistry  physical  agents  play  important  parts. 
By  heat  and  light  we  cause  bodies  to  combine,  and  by  heat 
and  light  we  decompose  them.  Electricity  tears  asunder 
the  locked  atoms  of  compounds.  Through  their  power 
of  separating  carbonic  acid  into  its  constituents,  the 
solar  beams  build  up  the  whole  vegetable  world,  and  by  it 
the  animal  world.  The  touch  of  the  self-same  beams 
causes  hydrogen  and  chlorine  to  unite  with  sudden  explo- 
sion, and  to  form  by  their  combination  a  powerful  acid. 
Thus  physics  and  chemistry  intermingle.  Physical  agents 
are,  however,  employed  by  the  chemist  as  a  means  to  an 
end  ;  while  in  physics  proper  the  laws  and  phenomena  of 
the  agents  themselves,  both  qualitative  and  quantitative, 
are  the  primary  objects  of  attention. 

My  duty  here  to-night  is  to  spend  an  hour  in  telling  how 
the  subject  of  magnetism  is  to  be  studied,  and  how  a  know- 
ledge of  it  is  to  be  imparted  to  others.  When  first  invited 
to  do  this,  I  hesitated  before  accepting  the  responsibility. 
It  would  be  easy  to  entertain  you  with  an  account  of  what 
natural  philosophy  has  accomplished.  I  might  point  to 
those  applications  of  science  regarding  which  we  hear  so 
much  in  the  newspapers,  and  which  we  often  find  mistaken 
for  science  itself.  I  might,  of  course,  ring  changes  on  the 
steam-engine  and  the  telegraph,  the  electrotype  and  the 
photograph,  the  medical  applications  of  physics,  and  the 
million  other  inlets  by  which  scientific  thought  filters  into 
practical  life.  That  would  be  easy  compared  with  the  task 
of  informing  you  how  you  are  to  make  the  study  of  physics 


MAGNETISM.  287 

the  instrument  of  your  own  culture ;  how  you  are  to  possess 
its  facts  and  make  them  living  seeds  which  shall  take  root 
and  grow  in  the  mind,  and  not  lie  like  dead  lumber  in  the 
storehouse  of  memory.  This  is  a  task  much  heavier  than 
the  mere  cataloguing  of  scientific  achievements  ;  and  it  is 
one  which,  feeling  my  own  want  of  time  and  power  to 
execute  it  aright,  I  might  well  hesitate  to  accept. 

But  let  me  sink  excuses,  and  attack  the  work  to  the 
best  of  my  ability.  First  and  foremost,  then,  I  would 
advise  you  to  get  a  knowledge  of  facts  from  actual  observ- 
ation. Facts  looked  at  directly  are  vital ;  when  they 
pass  into  words  half  the  sap  is  taken  out  of  them.  You 
wish,  for  example,  to  get  a  knowledge  of  magnetism ;  well, 
provide  yourself  with  a  good  book  on  the  subject,  if  you 
can,  but  do  not  be  content  with  what  the  book  tells  you  ; 
do  not  be  satisfied  with  its  descriptive  woodcuts ;  see  the 
operation  of  the  force  yourself.  Half  of  our  book  writers 
describe  experiments  which  they  never  made,  and  their 
descriptions  often  lack  both  force  and  truth  ;  but,  no  matter 
how  clever  or  conscientious  they  may  be,  their  written  words 
cannot  supply  the  place  of  actual  observation.  Every  fact 
has  numerous  radiations,  which  are  shorn  off  by  the  man 
who  describes  it.  Go,  then,  to  a  philosophical  instrument 
maker,  and  give,  according  to  your  means,  for  a  straight 
bar-magnet,  say,  half-a-crown,  or,  if  you  can  afford  it, 
five  shillings  for  a  pair  of  them  ;  or  get  a  smith  to  cut  a 
length  of  ten  inches  from  a  bar  of  steel  an  inch  wide  and 
half  an  inch  thick  ;  file  its  ends  decently,  harden  it,  and 
get  somebody  like  myself  to  magnetise  it.  Two  bar- 
magnets  are  better  than  one.  Procure  some  darning- 
needles  such  as  these.  Provide  yourself  also  with  a  little 
unspun  silk,  which  will  give  you  a  suspending  fibre  void  of 
torsion;  make  a  little  loop  of  paper,  or  of  wire,  and 
attach  your  fibre  to  it.  Do  it  neatly.  In  the  loop  place 
your  darning-needle,  and  bring  the  two  ends  or  polea,  as 


288  FRAGMENTS   OP   SCIENCE. 

they  are  called,  of  your  magnet  successively  up  to  either 
end  of  the  needle.  Both  the  poles,  you  find,  attract  both 
ends  of  the  needle.  Replace  the  needle  by  a  bit  of  annealed 
iron  wire;  the  same  effects  ensue.  Suspend  successively 
little  rods  of  lead,  copper,  silver,  or  brass,  of  wood,  glass, 
ivory,  or  whalebone ;  the  magnet  produces  no  sensible  effect 
upon  any  of  these  substances.  You  thence  infer  a  special 
property  in  the  case  of  steel  and  iron.  Multiply  your 
experiments,  however,  and  you  will  find  that  some  other 
substances,  besides  iron,  are  acted  upon  by  your  magnet. 
A.  rod  of  the  metal  nickel,  or  of  the  metal  cobalt,  from 
which  the  blue  colour  used  by  painters  is  derived,  exhibits 
powers  similar  to  those  observed  with  the  iron  and  steel. 

In  studying  the  character  of  the  force  you  may,  how- 
ever, confine  yourself  to  iron  and  steel,  which  are  always 
at  hand.  Make  your  experiments  with  the  darning- 
needle  over  and  over  again ;  operate  on  both  ends  of  the 
needle ;  try  both  ends  of  the  magnet.  Do  not  think  the 
work  stupid ;  you  are  conversing  with  Nature,  and  must 
acquire  a  certain  grace  and  mastery  over  her  language ; 
and  these  practice  can  alone  impart.  Let  every  move- 
ment be  made  with  care,  and  avoid  slovenliness  from  the 
outset.  In  every  one  of  your  experiments  endeavour  to 
feel  the  responsibility  of  a  moral  agent.  Experiment,  as 
I  have  said,  is  the  language  by  which  we  address  Nature, 
and  through  which  she  sends  her  replies ;  in  the  use  of 
this  language  a  lack  of  straightforwardness  is  as  possible, 
and  as  prejudicial,  as  in  the  spoken  language  of  the  tongue. 
If  you  wish  to  become  acquainted  with  the  truth  of 
Nature,  you  must  from  the  first  resolve  to  deal  with  her 
sincerely. 

Now  remove  your  needle  from  its  loop,  and  draw  it 
from  end  to  end  along  one  of  the  ends  of  the  magnet ; 
resuspend  it,  and  repeat  your  former  experiment.  You 
find  the  result  different.  You  now  find  that  each  ex- 


MAGNETISM.  289 

tremity  of  the  magnet  attracts  one  end  of  the  needle,  and 
repels  the  other.  The  simple  attraction,  observed  in  the 
first  instance,  is  now  replaced  by  a  dual  force.  Kepeat 
the  experiment  till  you  have  thoroughly  observed  the  ends 
which  attract  and  those  which  repel  each  other. 

Withdraw  the  magnet  entirely  from  the  vicinity  of 
your  needle,  and  leave  the  latter  freely  suspended  by  its 
fibre.  Shelter  it  as  well  as  you  can  from  currents  of  air, 
and  if  you  have  iron  buttons  on  your  coat,  or  a  steel  pen- 
knife in  your  pocket,  beware  of  their  action.  If  you  work 
at  night,  beware  of  iron  candlesticks,  or  of  brass  ones 
with  iron  rods  inside.  Freed  from  such  disturbances,  the 
needle  takes  up  a  certain  determinate  position.  It  sets 
its  length  nearly  north  and  south.  Draw  it  aside  from 
this  position  and  let  it  go.  After  several  oscillations  it 
will  again  come  to  it.  If  you  have  obtained  your  magnet 
from  a  philosophical  instrument  maker,  you  will  see  a 
mark  on  one  of  its  ends.  Supposing,  then,  that  you  drew 
your  needle  along  the  end  thus  marked,  and  that  the  eye- 
end  of  your  needle  was  the  last  to  quit  the  magnet,  you 
will  find  that  the  eye  turns  to  the  south,  the  point  of  the 
needle  turning  towards  the  north.  Make  sure  of  this, 
and  do  not  take  the  statement  on  my  authority. 

Now  take  a  second  darning-needle  like  the  first,  and 
magnetise  it  in  precisely  the  same  manner  :  freely  sus- 
pended it  also  will  turn  its  point  to  the  north  and  its  eye 
to  the  south.  Your  next  step  is  to  examine  the  action  of 
the  two  needles  which  you  have  thus  magnetised  upon 
each  other. 

Take  one  of  them  in  your  hand,  and  leave  the  othei 
suspended  ;  bring  the  eye-end  of  the  former  near  the  eye- 
end  of  the  latter ;  the  suspended  needle  retreats :  it  is 
repelled.  Make  the  same  experiment  with  the  two  points; 
you  obtain  the  same  result,  the  suspended  needle  is  re- 
pelled. Now  cause  the  dissimilar  ends  to  act  on  each 


290  FRAGMENTS   OF   SCIENCE. 

other — you  have  attraction— point  attracts  eye,  and  eyo 
attracts  point.  Prove  the  reciprocity  of  this  action  by 
removing  the  suspended  needle,  and  putting  the  other  in 
its  place.  You  obtain  the  same  result.  The  attraction, 
then,  is  mutual,  and  the  repulsion  is  mutual.  You  have 
thus  demonstrated  in  the  clearest  manner  the  funda- 
mental law  of  magnetism,  that  like  poles  repel,  and  that 
unlike  poles  attract,  each  other.  You  may  say  that  this  is 
all  easily  understood  without  doing  ;  but  do  it,  and  your 
knowledge  will  not  be  confined  to  what  I  have  uttered  here. 

I  have  said  that  one  end  of  your  magnet  has  a  mark 
upon  it ;  lay  several  silk  fibres  together,  so  as  to  get 
sufficient  strength,  or  employ  a  thin  silk  ribbon,  and  form 
a  loop  large  enough  to  hold  your  magnet.  Suspend  it; 
it  turns  its  marked  end  towards  the  north.  This  marked 
end  is  that  which  in  England  is  called  the  north  pole.  If 
a  common  smith  has  made  your  magnet,  it  will  be  con- 
venient to  determine  its  north  pole  yourself,  and  to  mark 
it  with  a  file.  You  vary  your  experiments  by  causing 
your  magnetised  darning-needle  to  attract  and  repel  your 
large  magnet ;  it  is  quite  competent  to  do  so.  In  mag- 
netising the  needle,  I  have  supposed  the  eye-end  to  be 
the  last  to  quit  the  marked  end  of  the  magnet ;  that  end 
of  the  needle  is  a  south  pole.  The  end  which  last  quits 
the  magnet  is  always  opposed  in  polarity  to  the  end  of 
the  magnet  with  which  it  has  been  in  contact.  Brought 
near  each  other  they  mutually  attract,  and  thus  demon- 
strate that  they  are  unlike  poles. 

You  may  perhaps  learn  all  this  in  a  single  hour  ;  but 
spend  several  at  it,  if  necessary ;  and  remember,  under- 
standing it  is  not  sufficient :  you  must  obtain  a  manual 
aptitude  in  addressing  Nature.  If  you  speak  to  your 
fellow-man  you  are  not  entitled  to  use  jargon.  Bad 
experiments  are  jargon  addressed  to  Nature,  and  just  as 
much  to  be  deprecated.  A  manual  dexterity  in  illustrat- 


MAGNETISM.  291 

ing  the  interaction  of  magnetic  poles  is  of  the  utmost 
importance  at  this  stage  of  your  progress ;  and  you  must 
not  neglect  attaining  this  power  over  your  implements. 
As  you  proceed,  moreover,  you  will  be  tempted  to  do 
more  than  I  can  possibly  suggest.  Thoughts  will  occur 
to  you  which  you  will  endeavour  to  follow  out ;  questions 
will  arise  which  you  will  try  to  answer.  The  same 
experiment  may  be  twenty  things  to  twenty  people. 
Having  witnessed  the  action  of  pole  on  pole,  through  the 
air,  you  will  perhaps  try  whether  the  magnetic  power 
is  not  to  be  screened  off.  You  use  plates  of  glass,  wood, 
slate,  pasteboard,  or  gutta-percha,  but  find  them  all 
pervious  to  this  wondrous  force.  One  magnetic  pole 
acts  upon  another  through  these  bodies  as  if  they  were 
not  present.  And  should  you  become  a  patentee  for  the 
regulation  of  ships'  compasses,  you  will  not  fall,  as  some 
projectors  have  done,  into  the  error  of  screening  off  the 
magnetism  of  the  ship  by  the  interposition  of  such  sub- 
stances. 

If  you  wish  to  teach  a  class  you  must  contrive  that  the 
effects  which  you  have  thus  far  witnessed  for  yourself 
shall  be  witnessed  by  twenty  or  thirty  pupils.  And  here 
your  private  ingenuity  must  come  into  play.  You  will 
attach  bits  of  paper  to  your  needles,  so  as  to  render  their 
movements  visible  at  a  distance,  denoting  the  north  and 
south  poles  by  different  colours,  say  green  and  red.  You 
may  also  improve  upon  your  darning-needle.  Take  a 
strip  of  sheet  steel — the  rib  of  a  lady's  stays  will  answer — 
heat  it  to  vivid  redness  and  plunge  it  into  cold  water. 
It  is  thereby  hardened ;  rendered,  in  fact,  almost  as  brittle 
as  glass.  Six  inches  of  this,  magnetised  in  the  manner  of 
the  darning-needle,  will  be  better  able  to  carry  your 
paper  indexes.  Having  secured  such  a  strip,  you  proceed 
thus : — 

Magnetise  a  small  sewing-needle  and  determine  its 
15 


292  FRAGMENTS   OP  SCIENCE. 

poles  ;  or,  break  half  an  inch,  or  an  inch,  off  your  magnet- 
ised darning-needle  and  suspend  it  by  a  fine  silk  fibre. 
The  sewing-needle,  or  the  fragment  of  the  darning-needle, 
is  now  to  be  used  as  a  test-needle,  to  examine  the  distri- 
bution of  the  magnetism  in  your  strip  of  steel.  Hold 
the  strip  upright  in  your  left  hand,  and  cause  the  test- 
needle  to  approach  the  lower  end  of  your  strip ;  one  end 
is  attracted,  the  other  is  repelled.  Eaise  your  needle 
along  the  strip  ;  its  oscillations,  which  at  first  were  quick, 
become  slower ;  opposite  the  middle  of  the  strip  they 
cease  entirely ;  neither  end  of  the  needle  is  attracted ; 
above  the  middle  the  test-needle  turns  suddenly  round, 
its  other  end  being  now  attracted.  Go  through  the 
experiment  thoroughly;  you  thus  learn  that  the  entire 
lower  half  of  the  strip  attracts  one  end  of  the  needle, 
while  the  entire  upper  half  attracts  the  opposite  end. 
Supposing  the  north  end  of  your  little  needle  to  be  that 
attracted  below,  you  infer  that  the  entire  lower  half  of 
your  magnetised  strip  exhibits  south  magnetism,  while 
the  entire  upper  half  exhibits  north  magnetism.  So  far, 
then,  you  have  determined  the  distribution  of  magnetism 
in  your  strip  of  steel. 

You  look  at  this  fact,  you  think  of  it ;  in  its  suggest- 
iveness  the  value  of  an  experiment  chiefly  consists.  The 
thought  arises :  '  What  will  occur  if  I  break  my  strip  of 
steel  across  in  the  middle  ?  Shall  I  obtain  two  magnets 
each  possessing  a  single  pole  ? '  Try  the  experiment ; 
break  your  strip  of  steel,  and  test  each  half  as  you  tested 
the  whole.  The  mere  presentation  of  its  two  ends  in 
succession  to  your  test-needle,  suffices  to  show  that  you 
have  not  a  magnet  with  a  single  pole — that  each  half 
possesses  two  poles  with  a  neutral  point  between  them. 
And  if  you  again  break  the  half  into  two  other  halves, 
you  will  find  that  each  quarter  of  the  original  strip 
exhibist  precisely  the  same  magnetic  distribution  as  the 


MAGNETISM.  293 

strip  itself.  You  may  continue  the  breaking  process  : 
no  matter  how  small  your  fragment  may  be,  it  still 
possesses  two  opposite  poles  and  a  neutral  point  between 
them.  Well,  your  hand  ceases  to  break  where  breaking 
becomes  a  mechanical  impossibility ;  but  does  the  mind 
stop  there  ?  No  :  you  follow  the  breaking  process  in  idea 
•when  you  can  no  longer  realise  it  in  fact ;  your  thoughts 
wander  amid  the  very  atoms  of  your  steel,  and  you  con- 
clude that  each  atom  is  a  magnet,  and  that  the  force 
exerted  by  the  strip  of  steel  is  the  mere  summation,  or 
resultant,  of  the  forces  of  its  ultimate  particles. 

Here,  then,  is  an  exhibition  of  power  which  we  can 
call  forth  at  pleasure  or  cause  to  disappear.  We  mag- 
netise our  strip  of  steel  by  drawing  it  along  the  pole  of  a 
magnet ;  we  can  demagnetise  it,  or  reverse  its  magnetism, 
by  properly  drawing  it  along  the  same  pole  in  the  oppo- 
site direction.  What,  then,  is  the  real  nature  of  this 
wondrous  change?  What  is  it  that  takes  place  among 
the  atoms  of  the  steel  when  the  substance  is  magnetised  ? 
The  question  leads  us  beyond  the  region  of  sense,  and 
into  that  of  imagination.  This  faculty,  indeed,  is  the 
divining-rod  of  the  man  of  science.  Not,  however,  an 
imagination  which  catches  its  creations  from  the  air,  but 
one  informed  and  inspired  by  facts;  capable  of  seizing 
firmly  on  a  physical  image  as  a  principle,  of  discerning 
its  consequences,  and  of  devising  means  whereby  these 
forecasts  of  thought  may  be  brought  to  an  experimental 
test.  If  such  a  principle  be  adequate  to  account  for  all 
the  phenomena — if  from  an  assumed  cause  the  observed 
acts  necessarily  follow,  we  call  the  assumption  a  theory, 
and,  once  possessing  it,  we  can  not  only  revive  at  pleasure 
facts  already  known,  but  we  can  predict  others  which  we 
have  never  seen.  Thus,  then,  in  the  prosecution  of 
physical  science,  our  powers  of  observation,  memory, 
imagination,  and  inference,  are  all  drawn  upon.  We 


294  FRAGMENTS   OF   SCIENCE. 

observe  facts  and  store  them  up;  imagination  broods 
upon  these  memories,  and  by  the  aid  of  reason  tries  to 
discern  their  interdependence.  The  theoretic  principle 
flashes  or  slowly  dawns  upon  the  mind ;  and  then  the 
deductive  faculty  interposes  to  carry  out  the  principle  to 
its  logical  consequences.  A  perfect  theory  gives  dominion 
over  natural  facts ;  and  even  an  assumption  which  can 
only  partially  stand  the  test  of  a  comparison  with  facts, 
may  be  of  eminent  use  in  enabling  us  to  connect  and 
classify  groups  of  phenomena.  The  theory  of  magnetic 
fluids  is  of  this  latter  character,  and  with  it  we  must  now 
make  ourselves  familiar. 

With  the  vietf  of  stamping  the  thing  more  firmly  on 
your  minds,  I  will  make  use  of  a  strong  and  vivid  image. 
In  optics,  red  and  green  are  called  complementary 
colours ;  their  mixture  produces  white.  Now  I  ask  you 
to  imagine  each  of  these  colours  to  possess  a  self-repulsive 
power  ;  that  red  repels  red,  and  that  green  repels  green  ; 
but  that  red  attracts  green  and  green  attracts  red,  the 
attraction  of  the  dissimilar  colours  being  equal  to  the 
repulsion  of  the  similar  ones.  Imagine  the  two  colours 
mixed  so  as  to  produce  white,  and  suppose  two  strips  of 
wood  painted  with  this  white  ;  what  will  be  their  action 
upon  each  other  ?  Suspend  one  of  them  freely  as  we 
suspended  our  darning-needle,  and  bring  the  other  near 
it ;  what  will  occur  ?  The  red  component  of  the  strip 
you  hold  in  your  hand  will  repel  the  red  component  of 
your  suspended  strip ;  but  then  it  will  attract  the  green, 
and,  the  forces  being  equal,  they  neutralise  each  other. 
In  fact,  the  least  reflection  shows  you  that  the  strips 
will  be  as  indifferent  to  each  other  as  two  unmagnetised 
darning-needles  would  be  under  the  same  circumstances. 

But  suppose,  instead  of  mixing  the  colours,  we  painted 
one  half  of  each  strip  from  centre  to  end  red,  and  the 
other  half  green,  it  is  perfectly  manifest  that  the  two 


MAGNETISM.  295 

strips  would  now  behave  towards  each  other  exactly  as 
our  two  magnetised  darning-needles — the  red  end  would 
repel  the  red  and  attract  the  green,  the  green  would  repel 
the  green  and  attract  the  red ;  so  that,  assuming  two 
colours  thus  related  to  each  other,  we  could  by  their 
mixture  produce  the  neutrality  of  an  unmagnetised  body, 
while  by  their  separation  we  could  produce  the  duality  of 
action  of  magnetised  bodies. 

But  you  have  already  anticipated  a  defect  in  my  con- 
ception ;  for  if  we  break  one  of  our  strips  of  wood  in  the 
middle  we  have  one  half  entirely  red,  and  the  other 
entirely  green,  and  with  these  it  would  be  impossible  to 
imitate  the  action  of  our  broken  magnet.  How,  then, 
must  we  modify  our  conception  ?  We  must  evidently 
suppose  each  molecule  of  wood  painted  green  on  one  face 
and  red  on  the  opposite  one.  The  resultant  action  of 
ail  the  atoms  would  then  exactly  resemble  the  action 
of  a  magnet.  Here  also,  if  the  two  opposite  colours  of 
each  atom  could  be  caused  to  mix  so  as  to  produce  white, 
we  should  have,  as  before,  perfect  neutrality. 

For  these  two  self-repellent  and  mutually  attractive 
colours,  substitute  in  your  minds  two  invisible  self-repellent 
and  mutually  attractive  fluids,  which  in  ordinary  steel  are 
mixed  to  form  a  neutral  compound,  but  which  the  act  of 
magnetisation  separates  from  each  other,  placing  the  op- 
posite fluids  on  the  opposite  faces  of  each  molecule.  You 
have  then  a  perfectly  distinct  conception  of  the  celebrated 
theory  of  magnetic  fluids.  The  strength  of  the  magnetism 
excited  is  supposed  to  be  proportional  to  the  quantity  of 
neutral  fluid  decomposed.  According  to  this  theory 
nothing  is  actually  transferred  from  the  exciting  magnet 
to  the  excited  steeL  The  act  of  magnetisation  consists  in 
the  forcible  separation  of  two  fluids  which  existed  in 
the  steel  before  it  was  magnetised,  but  which  then 
neutralised  each  other  by  their  coalescence.  And  if  you 


296  FRAGMENTS   OF   SCIENCE. 

test  your  magnet,  after  it  has  excited  a  hundred  pieces  of 
steel,  you  will  find  that  it  has  lost  no  force — no  more, 
indeed,  than  I  should  lose,  had  my  words  such  a  magnetic 
influence  on  your  minds  as  to  excite  in  them  a  strong 
resolve  to  study  natural  philosophy.  I  should  rather  be 
the  gainer  by  my  own  utterance,  and  by  the  reaction  of 
your  strength.  The  magnet  also  is  the  gainer  by  the 
reaction  of  the  body  which  it  magnetises. 

Look  now  to  your  excited  piece  of  steel ;  figure  each 
molecule  with  its  opposed  fluids  spread  over  its  oppo- 
site faces.  How  can  this  state  of  things  be  permanent  ? 
The  fluids,  by  hypothesis,  attract  each  other ;  what, 
then,  keeps  them  apart?  Why  do  they  not  instantly 
rush  together  across  the  equator  of  the  atom,  and  thus 
neutralise  each  other?  To  meet  this  question  philo- 
sophers have  been  obliged  to  infer  the  existence  of  a 
special  force,  which  holds  the  fluids  asunder.  They  call 
it  coercive  force  ;  and  it  is  found  that  those  kinds  of  steel 
which  offer  most  resistance  to  being  magnetised — which 
require  the  greatest  amount  of  l  coercion'  to  tear  their  fluids 
asunder — are  the  very  ones  which  offer  the  greatest  resist- 
ance to  the  reunion  of  the  fluids,  after  they  have  been 
once  separated.  Such  kinds  of  steel  are  most  suited  to 
the  formation  of  permanent  magnets.  It  is  manifest, 
indeed,  that  without  coercive  force  a  permanent  magnet 
would  not  be  at  all  possible. 

You  have  not  forgotten,  that  previous  to  magnetising 
your  darning-needle  both  its  ends  were  attracted  by  your 
magnet ;  and  that  both  ends  of  your  bit  of  iron  wire  were 
acted  upon  in  the  same  way.  Probably  also  long  before 
this  you  will  have  dipped  the  end  of  your  magnet  among 
iron  filings,  and  observed  how  they  cling  to  it ;  or  into  a 
nail-box,  and  found  how  it  drags  the  nails  after  it.  I  know 
very  well  that  if  you  are  not  the  slaves  of  routine,  you 
will  have  by  this  time  done  many  things  that  I  have  not 


MAGNETISM.  297 

told  you  to  do,  and  thus  multiplied  your  experience 
beyond  what  I  have  indicated.  You  are  almost  sure  to 
have  caused  a  bit  of  iron  to  hang  from  the  end  of  your 
magnet,  and  you  have  probably  succeeded  in  causing  a 
second  piece  to  attach  itself  to  the  first,  a  third  to  the 
second ;  until  finally  the  force  has  become  too  feeble  to 
bear  the  weight  of  more.  If  you  have  operated  with 
nails,  you  may  have  observed  that  the  points  and  edges 
hold  together  with  the  greatest  tenacity ;  and  that  a 
bit  of  iron  clings  more  firmly  to  the  corner  of  your 
magnet  than  to  one  of  its  flat  surfaces.  In  short, 
you  will  in  all  likelihood  have  enriched  your  expe- 
rience in  many  ways  without  any  special  direction 
from  me. 

Well,  the  magnet  attracts  the  nail,  and  that  nail  attracts 
a  second  one.  This  proves  that  the  nail  in  contact  with 
the  magnet  has  had  the  magnetic  quality  developed  in  it 
by  that  contact.  If  it  be  withdrawn  from  the  magnet  its 
power  to  attract  its  fellow  nail  ceases.  Contact,  however, 
is  not  necessary.  A  sheet  of  glass  or  paper,  or  a  space 
of  air,  may  exist  between  the  magnet  and  the  nail ;  the 
latter  is  still  magnetised,  though  not  so  forcibly  as  when 
in  actual  contact.  The  nail  thus  presented  to  the  magnet 
is  itself  a  temporary  magnet.  That  end  which  is  turned 
towards  the  magnetic  pole  has  the  opposite  magnetism  of 
the  pole  which  excites  it ;  the  end  most  remote  from  the 
pole  has  the  same  magnetism  as  the  pole  itself,  and 
between  the  two  poles  the  nail,  like  the  magnet,  possesses 
a  magnetic  equator. 

Conversant  as  you  now  are  with  the  theory  of  magnetic 
fluids,  you  have  already,  I  doubt  not,  anticipated  me  in 
imagining  the  exact  condition  of  iron  under  the  influ- 
ence of  the  magnet.  You  picture  the  iron  as  possessing 
the  neutral  fluid  in  abundance ;  you  picture  the  magnetic 
pole,  when  brought  near,  decomposing  the  fluid ;  repell- 


298  FRAGMENTS   OF   SCIENCE. 

ing  the  fluid  of  a  like  kind  with  itself,  and  attracting 
the  unlike  fluid  ;  thus  exciting  in  the  parts  of  the  iron 
nearest  to  itself  the  opposite  polarity.  But  the  iron  is 
incapable  of  becoming  a  permanent  magnet.  It  only 
shows  its  virtue  as  long  as  the  magnet  acts  upon  it. 
What,  then,  does  the  iron  lack  which  the  steel  possesses  ? 
It  lacks  coercive  force.  Its  fluids  are  separated  with 
ease  ;  but,  once  the  separating  cause  is  removed,  they  flow 
together  again,  and  neutrality  is  restored.  Your  imagina- 
tion must  be  quite  nimble  in  picturing  these  changes. 
You  must  be  able  to  see  the  fluids  dividing  and  reuniting, 
according  as  the  magnet  is  brought  near  or  withdrawn. 
Fixing  a  definite  pole  in  your  imagination,  you  must 
picture  the  precise  arrangement  of  the  two  fluids  with 
reference  to  this  pole.  And  you  must  not  only  be  well 
drilled  in  the  use  of  this  mental  imagery  yourself,  but 
you  must  be  able  to  arouse  the  same  pictures  in  the 
minds  of  your  pupils.  You  ought  to  satisfy  yourself  that 
they  possess  the  power  of  placing  magnets  and  iron 
in  various  positions,  and  describing  the  exact  magnetic 
state  of  the  iron  in  each  particular  case.  The  mere 
facts  of  magnetism  will  have  their  interest  immensely 
augmented  by  an  acquaintance  with  those  hidden  prin- 
ciples whereon  the  facts  depend.  Still,  while  you  use 
this  theory  of  magnetic  fluids,  to  track  out  the  pheno- 
mena and  link  them  together,  be  sure  to  tell  your  pupils 
that  it  is  to  be  regarded  as  a  symbol  merely, — a  symbol, 
moreover,  which  is  incompetent  to  cover  all  the  facts,1 
but  which  does  good  practical  service  whilst  we  are 
waiting  for  the  actual  truth. 

1  This  theory  breaks  down  when  applied  to  diamagnetic  bodies,  which 
are  repelled  by  magnets.  Like  soft  iron,  such  bodies  are  thrown  into  a 
state  of  temporary  excitement,  in  virtue  of  which  they  are  repelled ;  but  any 
attempt  to  explain  such  a  repulsion  by  the  decomposition  of  a  fluid  will 
demonstrate  ita  own  futility. 


MAGNETISM.  299 

This  state  of  excitement  into  which  the  annealed  iron 
is  thrown  by  the  influence  of  the  magnet,  is  sometimes 
called  'magnetisation  by  influence.'  More  commonly, 
however,  the  magnetism  is  said  to  be  '  induced '  in  the 
iron,  and  hence  this  mode  of  magnetising  is  called  '  mag- 
netic induction.'  Now,  there  is  nothing  theoretically 
perfect  in  Nature  :  there  is  no  iron  so  soft  as  not  to  possess 
a  certain  amount  of  coercive  force,  and  no  steel  so  hard  as 
not  to  be  capable,  in  some  degree,  of  magnetic  induction. 
The  quality  of  steel  is  in  some  measure  possessed  by  iron, 
and  the  quality  of  iron  is  shared  in  some  degree  by  steel. 
It  is  in  virtue  of  this  latter  fact  that  the  unmagnetised 
darning-needle  was  attracted  in  your  first  experiment; 
and  from  this  you  may  at  once  deduce  the  consequence  that, 
after  the  steel  has  been  magnetised,  the  repulsive  action 
of  a  magnet  must  be  always  less  than  its  attractive  action. 
For  the  repulsion  is  opposed  by  the  inductive  action  of 
the  magnet  on  the  steel,  while  the  attraction  is  assisted 
by  the  same  inductive  action.  Make  this  clear  to  your 
minds,  and  verify  it  by  your  experiments.  In  some  cases 
you  can  actually  make  the  attraction  due  to  the  temporary 
magnetism  overbalance  the  repulsion  due  to  the  per- 
manent magnetism,  and  thus  cause  two  poles  of  the  same 
kind  apparently  to  attract  each  other.  When,  however, 
good  hard  magnets  act  on  each  other  from  a  sufficient 
distance,  the  inductive  action  practically  vanishes,  and  the 
repulsion  of  like  poles  is  sensibly  equal  to  the  attraction 
of  unlike  ones. 

I  dwell  thus  long  on  elementary  principles,  because 
they  are  of  the  first  importance,  and  it  is  the  temptation 
of  this  age  of  unhealthy  cramming  to  neglect  them.  Now 
follow  me  a  little  farther.  In  examining  the  distribution 
of  magnetism  in  your  strip  of  steel  you  raised  the  needle 
slowly  from  bottom  to  top,  and  found  what  we  called  a 
neutral  point  at  the  centre.  Now  does  the  magnet  really 


300  FRAGMENTS    OF   SCIENCE. 

exert  no  influence  on  the  pole  presented  to  its  centre  ? 
Let  us  see. 

Let  s  N,  fig.  7,  be  our  magnet,  and  let  n  represent  a 
particle  of  north  magnetism  placed  exactly  opposite  the 
middle  of  the  magnet.  Of  course  this  is  an  imaginary 
case,  as  you  can  never  in  reality  thus  detach  your  north 
magnetism  from  its  neighbour.  What  is  the  action  of  the 
two  poles  of  the  magnet  on  n  ?  Your  reply  will  of  course 
be  that  the  pole  s  attracts  n  while  the  pole  N  repels  it.  Let 
the  magnitude  and  direction  of  the  attraction  be  expressed 
by  the  line  n  m,  and  the  magnitude  and  direction  of  the 
FIG.  7. 


repulsion  by  the  line  n  o.  Now,  the  particle  n  being 
equally  distant  from  s  and  N,  the  line  n  o,  expressing  the 
repulsion,  will  be  equal  to  ra  n,  which  expresses  the 
attraction.  Acted  upon  by  two  such  forces,  the  particle 
n  must  evidently  move  in  the  direction  p  n,  exactly 
midway  between  m  n  and  n  o.  Hence  you  see  that, 
although  there  is  no  tendency  of  the  particle  n  to  move 
towards  the  magnetic  equator,  there  is  a  tendency  on  its 
part  to  move  parallel  to  the  magnet.  If,  instead  of  a 
particle  of  north  magnetism,  we  placed  a  particle  of  south 
magnetism  opposite  to  the  magnetic  equator,  it  would 
evidently  be  urged  along  the  line  n  q ;  and  if,  instead  of 
two  separate  particles  of  magnetism,  we  place  a  little 
magnetic  needle,  containing  both  north  and  south  mag- 
netism, opposite  the  magnetic  equator,  its  south  pole 
being  urged  along  n  £,  and  its  north  along  n  p,  the  little 


MAGNETISM.  «01 

needle  will  be  compelled  to  set  itself  parallel  to  the 
magnet  s  N.  Make  the  experiment,  and  satisfy  yourselves 
that  this  is  a  true  deduction. 

Substitute  for  your  magnetic  needle  a  bit  of  iron  wire, 
devoid  of  permanent  magnetism,  and  it  will  set  itself  ex- 
actly as  the  needle  does.  Acted  upon  by  the  magnet,  the 
wire,  as  you  know,  becomes  a  magnet  and  behaves  as  such; 
it  will,  of  course,  turn  its  north  pole  towards  p,  and  south 
pole  towards  5,  just  like  the  needle. 

But  supposing  you  shift  the  position  of  your  particle  of 
north  magnetism,  and  bring  it  nearer  to  one  end  of  your 
magnet  than  to  the  other ;  the  forces  acting  on  the  particle 
are  no  longer  equal ;  the  nearest  pole  of  the  magnet  will 
act  more  powerfully  on  the  particle  than  the  more  distant 
one.  Let  s  N,  fig.  8,  be  the  magnet,  and  n  the  particle 
of  north  magnetism,  in  its  new  position.  Well,  it  is 
repelled  by  N,  and  attracted  by  s.  Let  the  repulsion  be 

Fro.  8. 


S  iv  H  N 

represented  in  magnitude  and  direction  by  the  line  n  o, 
and  the  attraction  by  the  shorter  line  n  m.  The  resultant 
of  these  two  forces  will  be  found  by  completing  the  par- 
allelogram m  n  o  p,  and  drawing  its  diagonal  n  p.  Along 
n  p,  then,  a  particle  of  north  magnetism  would  be  urged 
by  the  simultaneous  action  of  s  and  N.  Substituting  a 
particle  of  south  magnetism  for  n,  the  same  reasoning 
irould  lead  to  the  conclusion  that  the  particle  would  be 
urged  along  n  q.  If  we  place  at  n  a  short  magnetic 
needle,  its  north  pole  will  be  urged  along  n  p,  its  south 


302  FRAGMENTS   OF   SCIENCE. 

pole  along  n  g,  the  only  position  possible  to  the  needle, 
thus  acted  on,  being  along  the  line  p  q,  which  is  no  longer 
parallel  to  the  magnet.  Verify  this  deduction  by  actual 
experiment. 

In  this  way  we  might  go  round  the  entire  magnet ;  and, 
considering  its  two  poles  as  two  centres  from  which  the 
force  emanates,  we  could,  in  accordance  with  ordinary 
mechanical  principles,  assign  a  definite  direction  to  the 
magnetic  needle  at  every  particular  place.  And  substi- 
tuting, as  before,  a  bit  of  iron  wire  for  the  magnetic 
needle,  the  positions  of  both  will  be  the  same. 

Now,  I  think,  without  further  preface,  you  will  be  able 
to  comprehend  for  yourselves,  and  explain  to  others,  one 
of  the  most  interesting  effects  in  the  whole  domain  of 
magnetism.  Iron  filings  you  know  are  particles  of  iron, 
irregular  in  shape,  being  longer  in  some  directions  than 
in  others.  For  the  present  experiment,  moreover,  in- 
stead of  the  iron  filings,  very  small  scraps  of  thin  iron 
wire  might  be  employed.  I  place  a  sheet  of  paper  over 
the  magnet ;  it  is  all  the  better  if  the  paper  be  stretched 
on  a  wooden  frame,  as  this  enables  us  to  keep  it  quite 
level.  I  scatter  the  filings,  or  the  scraps  of  wire,  from  a 
sieve  upon  the  paper,  and  tap  the  latter  gently,  so  as  to 
liberate  the  particles  for  a  moment  from  its  friction. 
The  magnet  acts  on  the  filings  through  the  paper,  and  see 
how  it  arranges  them !  They  embrace  the  magnet  in  a 
series  of  beautiful  curves,  which  are  technically  called 
'  magnetic  curves,'  or  '  lines  of  magnetic  force.'  Does  the 
meaning  of  these  lines  yet  flash  upon  yon?  Set  your 
magnetic  needle,  or  your  suspended  bit  of  wire,  at  any 
point  of  one  of  the  curves,  and  you  will  find  the  direction 
of  the  needle,  or  of  the  wire,  to  be  exactly  that  of  the 
particle  of  iron,  or  of  the  magnetic  curve,  at  the  point. 
Go  round  and  round  the  magnet ;  the  direction  of  your 
needle  always  coincides  with  the  direction  of  the  curve 


MAONETIC   LINES  OP  FORCE. 
Fi-ot*  a  Photograph  by  Professor  MATB 


804  FRAGMENTS   OF   SCIENCE. 

on  which  it  is  placed.  These,  then,  are  the  lines  along 
which  a  particle  of  south  magnetism,  if  you  could  detach 
it,  would  move  to  the  north  pole,  and  a  bit  of  north  mag- 
netism to  the  south  pole.  They  are  the  lines  along  which 
the  decomposition  of  the  neutral  fluid  takes  place.  In 
the  case  of  the  magnetic  needle,  one  of  its  poles  being 
urged  in  one  direction,  and  the  other  pole  in  the  opposite 
direction,  the  needle  must  necessarily  set  itself  as  a 
tangent  to  the  curve.  I  will  not  seek  to  simplify  this 
subject  further.  If  there  be  anything  obscure  or  confused 
or  incomplete  in  my  statement,  you  ought  now,  by  patient 
thought,  to  be  able  to  clear  away  the  obscurity,  to  reduce 
the  confusion  to  order,  and  to  supply  what  is  needed  to 
render  the  explanation  complete.  Do  not  quit  the  subject 
until  you  thoroughly  understand  it;  and  if  you  are  then 
able  to  look  with  your  mind's  eye  at  the  play  of  forces 
around  a  magnet,  and  see  distinctly  the  operation  of  those 
forces  in  the  production  of  the  magnetic  curves,  the  time 
which  we  have  spent  together  will  not  have  been  spent  in 
vain. 

In  this  thorough  manner  we  must  master  our  materials, 
reason  upon  them,  and,  by  determined  study,  attain  to 
clearness  of  conception.  Facts  thus  dealt  with  exercise 
an  expansive  force  upon  the  boundaries  of  thought ; — they 
widen  the  mind  to  generalisation.  We  soon  recognise 
a  brotherhood  between  the  larger  phenomena  of  Nature 
and  the  minute  effects  which  we  have  observed  in  our 
private  chambers.  Why,  we  enquire,  does  the  magnetic 
needle  set  north  and  south  ?  Evidently  it  is  compelled 
to  do  so  by  the  earth  ;  the  great  globe  which  we  inherit 
is  itself  a  magnet.  Let  us  learn  a  little  more  about 
it  By  means  of  a  bit  of  wax,  or  otherwise,  attach  the 
middle  point  of  your  silk  fibre  to  your  magnetic  needle ; 
the  needle  will  thus  be  uninterfered  with  by  the 
paper  loop,  and  will  enjoy  to  some  extent  a  power  of 


MAGNETISM.  305 

'  dipping '  its  point,  or  its  eye,  below  the  horizon.  Lay 
your  magnet  on  a  table,  and  hold  the  needle  over  the 
equator  of  the  magnet.  The  needle  sets  horizontal. 
Move  it  towards  the  north  end  of  the  magnet ;  the  south 
end  of  the  needle  dips,  the  dip  augmenting  as  you  approach 
the  north  pole,  over  which  the  needle,  if  free  to  move, 
will  set  itself  exactly  vertical.  Move  it  back  to  the  centre, 
it  resumes  its  horizontality ;  pass  it  on  towards  the  south 
pole,  its  north  end  now  dips,  and  directly  over  the  south 
pole  the  needle  becomes  vertical,  its  north  end  being  now 
turned  downwards.  Thus  we  learn  that  on  the  one  side 
of  the  magnetic  equator  the  north  end  of  the  needle 
dips ;  on  the  other  side  the  south  end  dips,  the  dip  vary- 
ing from  nothing  to  90°.  If  we  go  to  the  equatorial 
regions  of  the  earth  with  a  suitably  suspended  needle  we 
shall  find  there  the  position  of  the  needle  horizontal.  If 
we  sail  north  one  end  of  the  needle  dips ;  if  we  sail  south 
the  opposite  end  dips ;  and  over  the  north  or  south  terres- 
trial magnetic  pole  the  needle  sets  vertical.  The  south 
magnetic  pole  has  not  yet  been  found,  but  Sir  James  Eoss 
discovered  the  north  magnetic  pole  on  June  1,  1831.  In 
this  manner  we  establish  a  complete  parallelism  between 
the  action  of  the  earth  and  that  of  an  ordinary  magnet. 

The  terrestrial  magnetic  poles  do  not  coincide  with 
the  geographical  ones;  nor  does  the  earth's  magnetic 
equator  quite  coincide  with  the  geographical  equator. 
The  direction  of  the  magnetic  needle  in  London,  which  is 
called  the  magnetic  meridian,  encloses  an  angle  of  24° 
with  the  true  astronomical  meridian,  this  angle  being 
called  the  Declination  of  the  needle  for  London.  The 
north  pole  of  the  needle  now  lies  to  the  west  of  the 
true  meridian ;  the  declination  is  westerly.  In  the  year 
1660,  however,  the  declination  was  nothing,  while  before 
that  time  it  was  easterly.  All  this  proves  that  the  earth's 
magnetic  constituents  are  gradually  changing  their  dis- 


306  FRAGMENTS   OP   SCIENCE. 

tribution.  This  change  is  very  slow ;  it  is  technically 
called  the  secular  change,  and  the  observation  of  it  has 
not  yet  extended  over  a  sufficient  period  to  enable  us  to 
guess,  even  approximately,  at  its  laws. 

Having  thus  discovered,  to  some  extent,  the  secret  of 
the  earth's  power,  we  can  turn  it  to  account.  I  hold  in 
my  hand  a  poker  formed  of  good  soft  iron ;  it  is  now  in 
the  line  of  dip — a  tangent,  in  fact,  to  the  earth's  line  of 
magnetic  force.  The  earth,  acting  as  a  magnet,  is  at  this 
moment  constraining  the  two  fluids  of  the  poker  to 
separate,  making  the  lower  end  of  the  poker  a  north  pole, 
and  the  upper  end  a  south  pole.  Mark  the  experiment : 
I  hold  the  knob  uppermost,  and  it  attracts  the  north 
end  of  a  magnetic  needle.  I  now  reverse  the  poker, 
bringing  its  knob  undermost ;  the  knob  is  now  a  north 
pole  and  attracts  the  south  end  of  a  magnetic  needle. 
Gret  such  a  poker  and  carefully  repeat  this  experiment ; 
satisfy  yourselves  that  the  fluids  shift  their  position,  ac- 
cording to  the  manner  in  which  the  poker  is  presented  to 
the  earth.  It  has  already  been  stated  that  the  softest  iron 
possesses  a  certain  amount  of  coercive  force.  The  earth, 
at  this  moment,  finds  in  this  force  an  antagonist  which 
opposes  the  full  decomposition  of  the  neutral  fluid.  The 
component  fluids  may  be  figured  as  meeting  an  amount  of 
friction,  or  possessing  an  amount  of  adhesion,  which  pre- 
vents them  from  gliding  over  the  molecules  of  the  poker. 
Can  we  assist  the  earth  in  this  case  ?  If  we  wish  to  re- 
move the  residue  of  a  powder  from  the  interior  surface  of 
a  glass  to  which  the  powder  clings,  we  invert  the  glass, 
tap  it,  loosen  the  hold  of  the  powder,  and  thus  enable  the 
force  of  gravity  to  pull  it  down.  So  also  by  tapping  the 
end  of  the  poker  we  loosen  the  adhesion  of  the  fluids  to  the 
molecules  and  enable  the  earth  to  pull  them  apart.  But, 
what  is  the  consequence  ?  The  portion  of  fluid  which  has 
been  thus  forcibly  dragged  over  the  molecules  refuses  to 


MAGNETISM.  307 

return  when  the  poker  has  been  removed  from  the  line  of 
dip ;  the  iron,  as  you  see,  has  become  a  permanent  magnet. 
By  reversing  its  position  and  tapping  it  again  we  reverse 
its  magnetism.  A  thoughtful  and  competent  teacher 
will  well  know  how  to  place  these  remarkable  facts  before 
his  pupils  in  a  manner  which  will  excite  their  interest. 
By  the  use  of  sensible  images,  more  or  less  gross,  he  will 
first  give  those  whom  he  teaches  definite  conceptions,  puri- 
fying these  conceptions  more  and  more,  as  the  minds  of  his 
pupils  become  more  capable  of  abstraction.  He  will  cause 
his  logic  to  run  like  a  line  of  light  through  these  images, 
and  by  thus  acting  he  will  cause  his  boys  to  march  at 
his  side  with  a  profit  and  a  joy  which  the  mere  exhibition 
of  facts  without  principles,  or  the  appeal  to  the  bodily 
senses  and  the  power  of  memory  alone,  could  never  inspire. 


As  an  expansion  of  the  note  at  p.  259,  the  following  extract  may  find  a 
place  here : — 

'It  is  well  known  that  a  voltaic  current  exerts  an  attractive  force  upon 
a  second  current,  flowing  in  the  same  direction ;  and  that  when  the  direc- 
tions are  opposed  to  each  other  the  force  exerted  is  a  repulsive  one.  By 
coiling  wires  into  spirals,  Ampere  was  enabled  to  make  them  produce  all 
the  phenomena  of  attraction  and  repulsion  exhibited  by  magnets,  and  from 
this  it  was  but  a  step  to  his  celebrated  theory  of  molecular  currents.  He 
supposed  the  molecules  of  a  magnetic  body  to  be  surrounded  by  such  currents, 
which,  however,  in  the  natural  state  of  the  body  mutually  neutralised  each 
other,  on  account  of  their  confused  grouping.  The  act  i/f  magnetisation  he 
supposed  to  consist  in  setting  these  molecular  currents  parallel  to  each  other ; 
and,  starting  from  this  principle,  he  reduced  all  the  phenomena  of  magnet- 
ism to  the  mutual  action  of  electric  currents. 

1  If  we  reflect  upon  the  experiments  recorded  in  the  foregoing  pages  from 
first  to  last,  we  can  hardly  fail  to  be  convinced  that  diamagnetic  bodies 
operated  on  by  magnetic  forces  possess  a  polarity  "  the  same  in  kind  as,  but 
the  reverse  in  direction  of,  that  acquired  by  magnetic  bodies."  But  if  this 
be  the  case,  how  are  we  to  conceive  the  physical  mechanism  of  this  polarity  ? 


308  FRAGMENTS   OF   SCIENCE. 

According  to  Coulomb's  and  Poisson's  theory,  the  act  of  magnetisation 
consists  in  the  decomposition  of  a  neutral  magnetic  fluid  ;  the  north  pole  of 
a  magnet,  for  example,  possesses  an  attraction  for  the  south  fluid  of  a  piece 
of  soft  iron  submitted  to  its  influence,  draws  the  said  fluid  towards  it,  and 
•with  it  the  material  particles  with  which  the  fluid  is  associated.  To  account 
for  diamagnetic  phenomena  this  theory  seems  to  fail  altogether ;  according 
to  it,  indeed,  the  oft-used  phrase,  "  a  north  pole  exciting  a  north  pole,  and 
a  south  pole  a  south  pole,"  involves  a  contradiction.  For  if  the  north  fluid 
be  supposed  to  be  attracted  towards  the  influencing  north  pole,  it  is  absurd 
to  suppose  that  its  presence  there  could  produce  repulsion.  The  theory  of 
Ampere  is  equally  at  a  loss  to  explain  diamagnetic  action  ;  for  if  we  suppose 
the  particles  of  bismuth  surrounded  by  molecular  currents,  then,  according 
to  all  that  is  known  of  electro-dynamic  laws,  these  currents  would  set  them- 
selves parallel  to,  and  in  the  same  direction  as,  those  of  the  magnet,  and 
hence  attraction,  and  not  repulsion,  would  be  the  result.  The  fact,  however, 
of  this  not  being  the  case,  proves  that  these  molecular  currents  are  not  the 
mechanism  by  which  diamagnetic  hiduction  is  effected.  The  consciousness 
of  this.  I  doubt  not,  drove  M.  Weber  to  the  assumption  that  the  phenomena 
of  diamagnetism  are  produced  by  molecular  currents,  not  directed,  but  actu- 
ally excited  in  the  bismuth  by  the  magnet.  Such  induced  currents  would, 
according  to  known  laws,  have  a  direction  opposed  to  those  of  the  inducing 
magnet,  and  hence  wculd  produce  the  phenomena  of  repulsion.  To  carry 
out  the  assumption  here  made,  M.  Weber  is  obliged  to  suppose  that  the 
molecules  of  diamagnetic  bodies  are  surrounded  by  channels,  in  which  the 
induced  molecular  currents,  once  excited,  continue  to  flow  without  resist 
ance.' — Diamagnetism  and  Magne-crystallic  Action,  p.  136-7. 


XII. 
DEATH  BY  LIGHTNING. 

T)EOPLE  in  general  imagine,  when  they  think  at  all 
JL  about  the  matter,  that  an  impression  upon  the  nerves 
— a  blow,  for  example,  or  the  prick  of  a  pin — is  felt  at  the 
moment  it  is  inflicted.  But  this  is  not  the  case.  The 
seat  of  sensation  is  the  brain,  and  to  it  the  intelligence  of 
any  impression  made  upon  the  nerves  has  to  be  transmitted 
before  this  impression  can  become  manifest  in  conscious- 
ness. The  transmission,  moreover,  requires  time,  and  the 
consequence  is,  that  a  wound  inflicted  on  a  portion  of  the 
body  distant  from  the  brain  is  more  tardily  appreciated 
than  one  inflicted  adjacent  to  the  brain.  By  an  extremely 
ingenious  experimental  arrangement,  Helmholtz  has  de- 
termined the  velocity  of  this  nervous  transmission,  and 
finds  it  to  be  about  one  hundred  feet  a  second,  or  less 
than  one-tenth  of  the  velocity  of  sound  in  air.  If,  there- 
fore, a  whale  fifty  feet  long  were  wounded  in  the  tail,  it 
would  not  be  conscious  of  the  injury  till  half  a  second 
after  the  wound  had  been  inflicted.1  But  this  is  not  the 
only  ingredient  in  the  delay.  There  can  scarcely  be  a 
doubt  that  to  every  act  of  consciousness  belongs  a  deter- 
minate molecular  arrangement  of  the  brain — that  every 
thought  or  feeling  has  its  physical  correlative  in  that 

1  A  most  admirable  lecture  on  the  velocity  of  nervous  transmission  has 
been  published  by  Dr.  Du  Bois  Eeymond  in  the  '  Proceedings  of  the  Royal 
Institution '  for  1 866,  vol.  iv.  p.  575. 


810  FKAGMENTS   OF  SCIENCE. 

organ ;  and  nothing  can  be  more  certain  than  that  every 
physical  change,  whether  molecular  or  mechanical,  requires 
time  for  its  accomplishment.  So  that,  besides  the  interval 
of  transmission,  a  still  further  time  is  necessary  for  the 
brain  to  put  itself  in  order — for  its  molecules  to  take  up 
the  motions  or  positions  necessary  to  the  completion  of 
consciousness.  Helmholtz  considers  that  one-ter.th  of  a 
second  is  demanded  for  this  purpose.  Thus,  in  the  case 
of  the  whale  above  supposed,  we  have  first  half  a  second 
consumed  in  the  transmission  of  the  intelligence  through 
the  sensor  nerves  to  the  head,  one-tenth  of  a  second 
consumed  by  the  brain  in  completing  the  arrangements 
necessary  to  consciousness,  and,  if  the  velocity  of  trans- 
mission through  the  motor  be  the  same  as  that  through 
the  sensor  nerves,  half  a  second  in  sending  a  command  to 
the  tail  to  defend  itself.  Thus  one  second  and  a  tenth 
would  elapse  before  an  impression  made  upon  its  caudal 
nerves  could  be  responded  to  by  a  whale  fifty  feet  long. 

Now,  it  is  quite  conceivable  that  an  injury  might  be 
inflicted  which  would  render  the  nerves  unfit  to  be  the 
conductors  of  the  motion  which  results  in  sensation  ;  and 
if  such  a  thing  occurred,  no  matter  how  severe  the  injury 
might  be,  we  should  not  be  conscious  of  it.  Or  it  may 
be,  that  long  before  the  time  required  by  the  brain  to 
complete  the  arrangements  necessary  to  consciousness,  its 
power  of  arrangement  might  be  wholly  suspended.  In 
such  a  case  also,  though  the  injury  might  be  of  a  nature 
to  cause  death,  this  would  occur  without  feeling  of  any 
kind.  Death  in  this  case  would  be  simply  the  sudden 
negation  of  life,  without,  any  intervention  of  consciousness 
whatever. 

Doubtless  there  are  many  kinds  of  death  of  this  cha- 
racter. The  passage  of  a  musket-bullet  through  the  brain 
is  a  case  in  point ;  and  the  placid  aspect  of  a  man  thus 
killed  is  in  perfect  accordance  with  the  conclusion  which 


DEATH   BY   LIGHTNING.  3tl 

might  be  drawn  a  'priori  from  the  experiments  of  Helm- 
holtz.  Cases  of  insensibility,  moreover,  are  not  uncommon 
which  do  not  result  in  death,  and  after  which  the  persons 
affected  have  been  able  to  testify  that  no  pain  was  felt 
prior  to  the  loss  of  consciousness. 

The  time  required  for  a  rifle-bullet  to  pass  clean  through 
a  man's  head  may  be  roughly  estimated  at  a  thousandth 
of  a  second.  Here,  therefore,  we  should  have  no  room 
for  sensation,  and  death  would  be  painless.  But  there 
are  other  actions  which  far  transcend  in  rapidity  that  of 
the  rifle-bullet.  A  flash  of  lightning  cleaves  a  cloud, 
appearing  and  disappearing  in  less  than  a  hundred- 
thousandth  of  a  second,  and  the  velocity  of  electricity  is 
such  as  would  carry  it  in  a  single  second  over  a  distance 
almost  equal  to  that  which  separates  the  earth  and  moon. 
It  is  well  known  that  a  luminous  impression  once  made 
upon  the  retina  endures  for  about  one-sixth  of  a  second, 
and  that  this  is  the  reason  why  we  see  a  ribbon  of  light 
when  a  glowing  coal  is  caused  to  pass  rapidly  through  the 
air.  A  body  illuminated  by  an  instantaneous  flash  con- 
tinues to  be  seen  for  the  sixth  of  a  second  after  the  flash 
has  become  extinct ;  and  if  the  body  thus  illuminated  be 
in  motion,  it  appears  at  rest  at  the  place  where  the  flash 
falls  upon  it.  The  colour-top  is  familiar  to  most  of  us. 
By  this  instrument  a  disk  with  differently-coloured  sectors 
is  caused  to  rotate  rapidly ;  the  colours  blend  together, 
and, -if  they  are  chosen  in  the  proper  proportions,  when 
the  motion  is  sufficiently  rapid  the  disk  appears  white. 
Such  a  top,  rotating  in  a  dark  room  and  illuminated  by 
an  electric  spark,  appears  motionless,  each  distinct  colour 
being  clearly  seen.  Professor  Dove  has  found  that  a  flash 
of  lightning  produces  the  same  effect.  During  a  thunder- 
storm he  put  a  colour-top  in  exceedingly  rapid  motion, 
and  found  that  every  flash  revealed  the  top  as  a  motion- 
less object  with  its  colours  distinct.  If  illuminated  solely 


812  FEAGMENTS  OF  SCIENCE. 

by  a  flash  of  lightning,  the  motion  of  all  bodies  on  the 
earth's  surface  would,  as  Dove  has  remarked,  appear  sus- 
pended. A  cannon-ball,  for  example,  would  have  its  flight 
apparently  arrested,  and  would  seem  to  hang  motionless 
in  space  as  long  as  the  luminous  impression  which  revealed 
the  ball  remained  upon  the  eye. 

If,  then,  a  rifle-bullet  move  with  sufficient  rapidity  to 
destroy  life  without  the  interposition  of  sensation,  much 
more  is  a  flash  of  lightning  competent  to  produce  this 
effect.  Accordingly,  we  have  well-authenticated  cases  of 
people  being  struck  senseless  by  lightning  who,  on  recovery, 
had  no  memory  of  pain.  The  following  circumstantial 
case  is  described  by  Hemmer : — 

On  June  30,  1788,  a  soldier  in  the  neighbourhood  of 
Mannneim,  being  overtaken  by  rain,  placed  himself  under 
a  tree,  beneath  which  a  woman  had  previously  taken 
shelter.  He  looked  upwards  to  see  whether  the  branches 
were  thick  enough  to  afford  the  required  protection,  and, 
in  doing  so,  was  struck  by  lightning,  and  fell  senseless  to 
the  earth.  The  woman  at  his  side  experienced  the  shock 
in  her  foot,  but  was  not  struck  down.  Some  hours  after- 
wards the  man  revived,  but  remembered  nothing  about 
what  had  occurred,  save  the  fact  of  his  looking  up  at  the 
branches.  This  was  his  last  act  of  consciousness,  and  he 
passed  from  the  conscious  to  the  unconscious  condition 
without  pain.  The  visible  marks  of  a  lightning  stroke  are 
usually  insignificant :  the  hair  is  sometimes  burnt ;  slight 
wounds  are  observed ;  while,  in  some  instances,  a  red 
streak  marks  the  track  of  the  discharge  over  the  skin. 

Under  ordinary  circumstances,  the  discharge  from  a 
small  Leyden  jar  is  exceedingly  unpleasant  to  me.  Some 
time  ago  I  happened  to  stand  in  the  presence  of  a 
numerous  audience,  with  a  battery  of  fifteen  large  Leyden 
jars  charged  beside  me.  Through  some  awkwardness  on 
my  part,  I  touched  a  wire  leading  from  the  battery,  and 


DEATH  BY  LIGHTNING.  318 

the  discharge  went  through  my  body.  Life  was  abso- 
lutely blotted  out  for  a  very  sensible  interval,  without  a 
trace  of  pain.  In  a  second  or  so  consciousness  returned ; 
I  saw  myself  in  the  presence  of  the  audience  and  ap- 
paratus, and,  by  the  help  of  these  external  appearances, 
immediately  concluded  that  I  had  received  the  battery 
discharge.  The  intellectual  consciousness  of  my  position 
was  restored  with  exceeding  rapidity,  but  not  so  the 
optical  consciousness.  To  prevent  the  audience  from 
being  alarmed,  I  observed  that  it  had  often  been  my 
desire  to  receive  accidentally  such  a  shock,  and  that  my 
wish  had  at  length  been  fulfilled.  But,  while  making  this 
remark,  the  appearance  which  my  body  presented  to  my- 
self was  that  of  a  number  of  separate  pieces.  The  arms, 
for  example,  were  detached  from  the  trunk,  and  seemed 
suspended  in  the  air.  In  fact,  memory  and  the  power 
of  reasoning  appeared  to  be  complete  long  before  the 
optic  nerve  was  restored  to  healthy  action.  But  what  I 
wish  chiefly  to  dwell  upon  here  is,  the  absolute  painless- 
ness  of  the  shock ;  and  there  cannot  be  a  doubt  that,  to 
a  person  struck  dead  by  lightning,  the  passage  from  life 
to  death  occurs  without  consciousness  being  in  the  least 
degree  implicated.  It  is  an  abrupt  stoppage  of  sensation, 
unaccompanied  by  a  pang. 

July  8,  1865. 


FRAGMENTS    OF   SCIENCE. 


XIII. 
SCIENCE  AND  THE  'SPIRITS? 

THEIE  refusal  to  investigate  '  spiritual  phenomena  is 
often  urged  as  a  reproach  to  scientific  men.  I  kere 
propose  to  give  a  sketch  of  an  attempt  to  apply  to  the 
4  phenomena '  those  methods  of  enquiry  which  are  found 
available  in  dealing  with  natural  truth. 

Some  time  ago,  when  the  spirits  were  particularly 
active  in  this  country,  a  celebrated  philosopher  was  in- 
vited, or  rather  entreated,  by  one  of  his  friends  to  meet 
and  question  them.  He  had,  however,  already  made 
their  acquaintance,  and  did  not  wish  to  renew  it.  I  had 
not  been  so  privileged,  and  he  therefore  kindly  arranged 
a  transfer  of  the  invitation  to  me.  The  spirits  themselves 
named  the  time  of  meeting,  and  I  was  conducted  to  the 
place  at  the  day  and  hour  appointed. 

Absolute  unbelief  in  the  facts  was  by  no  means  my 
condition  of  mind.  On  the  contrary,  I  thought  it  pro- 
bable that  some  physical  principle,  not  evident  to  the 
spiritualists  themselves,  might  underlie  their  manifesta- 
tions. Extraordinary  effects  are  produced  by  the  accu- 
mulation of  small  impulses.  Galileo  set  a  heavy  pendu- 
lum in  motion  by  the  well-timed  puffs  of  his  breath. 
Ellicot  set  one  clock  going  by  the  ticks  of  another,  even 
when  the  two  clocks  were  separated  by  a  wall.  Precon- 
ceived notions  can,  moreover,  vitiate,  to  an  extraordinary 
degree,  the  testimony  of  even  veracious  persons.  Hence 


SCIENCE   AND   THE  'SPIRITS/  315 

my  desire  to  witness  those  extraordinary  phenomena,  the 
existence  of  which  seemed  placed  beyond  a  doubt  by  the 
known  veracity  of  those  who  had  witnessed  and  described 
them.  The  meeting  took  place  at  a  private  residence  in 
the  neighbourhood  of  London.  My  host,  his  intelligent 
wife,  and  a  gentleman  who  may  be  called  X.,  were  in  the 
house  when  I  arrived.  I  was  informed  that  the  '  medium 
had  not  yet  made  her  appearance  ;  that  she  was  sensitive, 
and  might  resent  suspicion.  It  was  therefore  requested 
that  the  tables  and  chairs  should  be  examined  before  her 
arrival,  in  order  to  be  assured  that  there  was  no  trickery 
in  the  furniture.  This  was  done  ;  and  I  then  first  learned 
that  my  hospitable  host  had  arranged  that  the  seance 
should  be  a  dinner-party.  This  was  to  me  an  unusual 
form  of  investigation ;  but  I  accepted  it,  as  one  of  the 
accidents  of  the  occasion. 

The  'medium'  arrived — a  delicate- looking  young 
lady,  who  appeared  to  have  suffered  much  from  ill-health. 
I  took  her  to  dinner  and  sat  close  beside  her.  Facts  were 
absent  for  a  considerable  time,  a  series  of  very  wonderful 
narratives  supplying  their  place.  The  duty  of  belief  on 
testimony  was  frequently  insisted  on.  X.  appeared  to  be 
a  chosen  spiritual  agent,  and  told  us  many  surprising 
things.  He  affirmed  that,  when  he  took  a  pen  in  his 
hand,  an  influence  ran  from  his  shoulder  downwards,  and 
impelled  him  to  write  oracular  sentences.  I  listened  for 
a  time,  offering  no  observation.  '  And  now,'  continued 
X.,  '  this  power  has  so  risen  as  to  reveal  to  me  the  thoughts 
of  others.  Only  this  morning  I  told  a  friend  what  he  was 
thinking  of,  and  what  he  intended  to  do  during  the  day.' 
Here,  I  thought,  is  something  that  can  be  at  once  tested. 
E  said  immediately  to  X. :  '  If  you  wish  to  win  to  your 
cause  an  apostle,  who  will  proclaim  your  principles  to  the 
world  without  fear,  tell  me  what  I  am  now  thinking  of. 
X.  reddened,  and  did  not  tell  me  my  thought. 
16 


816  FKAGMEXTS   OF   SCIENCE. 

Some  time  previously  I  had  visited  Baron  Reichen- 
bach,  in  Vienna,  and  I  now  asked  the  young  lady  who 
sat  beside  me,  whether  she  could  see  any  of  the  curious 
things  which  he  describes — the  light  emitted  by  crystals, 
for  example  ?  Here  is  the  conversation  which  followed, 
as  extracted  from  my  notes,  written  on  the  day  following 
the  seance. 

Medium. — ' Oh,  yes ;  but  I  see  light  around  all 
bodies.' 

/. — '  Even  in  perfect  darkness  ? ' 

Medium. — 'Yes;  I  see  luminous  atmospheres  round 
all  people.  The  atmosphere  which  surrounds  Mr.  R.  C. 
•would  fill  this  room  with  light.' 

/. — *  You  are  aware  of  the  effects  ascribed  by  Baron 
Reichenbach  to  magnets  ? ' 

Medium. — '  Yes ;  but  a  magnet  makes  me  terribly 
ill.' 

/. — 'Am  I  to  understand  that,  if  this  room  were 
perfectly  dark,  you  could  tell  whether  it  contained  a 
magnet,  without  being  informed  of  the  fact  ? ' 

Medium.  —  1 1  should  know  of  its  presence  on  entering 
the  room.' 

/.—'How?' 

Medium. — '  I  should  be  rendered  instantly  ill.' 

/. — '  How  do  you  feel  to-day  ?  ' 

Medium. — '  Particularly  well ;  I  have  not  been  so 
well  for  months.' 

/. — '  Then,  may  I  ask  you  whether  there  is,  at  the 
present  moment,  a  magnet  in  my  possession  ? ' 

The  young  lady  looked  at  me,  blushed,  and  stam- 
mered, 

'  No  ;  I  am  not  en  rapport  with  you.' 

/  sat  at  her  right  hand,  and  a  left-hand  pocket,  with- 
in six  inches  of  her  person,  contained  a  magnet. 

Our  host  here  deprecated  discussion,  as  it  '  exhausted 


SCIENCE  AND   THE   'SPIRITS.'  317 

the  medium.'  The  wonderful  narratives  were  resumed ; 
but  I  had  narratives  of  my  own  quite  as  wonderful. 
These  spirits,  indeed,  seemed  clumsy  creations,  compared 
with  those  with  which  my  own  researches  had  made  me 
familiar.  I  therefore  began  to  match  the  wonders  re- 
lated to  me  by  other  wonders.  A  lady  present  discoursed 
on  spiritual  atmospheres,  which  she  could  see  as  beautiful 
colours  when  she  closed  her  eyes.  I  professed  myself 
able  to  see  similar  colours,  and,  more  than  that,  to  be 
able  to  see  the  interior  of  my  own  eyes.  The  medium 
affirmed  that  she  could  see  actual  waves  of  light  coming 
from  the  sun.  I  retorted  that  men  of  science  could  tell 
the  exact  number  of  waves  emitted  in  a  second,  and  also 
their  exact  length.  The  medium  spoke  of  the  per- 
formances of  the  spirits  on  musical  instruments.  I  said 
that  such  performance  was  gross,  in  comparison  with  a 
kind  of  music  which  had  been  discovered  some  time  pre- 
viously by  a  scientific  man.  Standing  at  a  distance  of 
twenty  feet  from  a  jet  of  gas,  he  could  command  the 
flame  to  emit  a  melodious  note  ;  it  would  obey,  and  con- 
tinue its  song  for  hours.  So  loud  was  the  music  emitted 
by  the  gas-flame,  that  it  might  be  heard  by  an  assembly 
of  a  thousand  people.  These  were  acknowledged  to  be 
as  great  marvels  as  any  of  those  of  spiritdom.  The  spirits 
were  then  consulted,  and  I  was  pronounced  to  be  a  first- 
class  medium. 

During  this  conversation  a  low  knocking  was  heard 
from  time  to  time  under  the  table.  These  were  the 
spirits'  knocks.  I  was  informed  that  one  knock,  in 
answer  to  a  question,  meant  '  No ; '  that  two  knocks  meant 
'  Not  yet ; '  and  that  three  knocks  meant  c  Yes.'  In  answer 
to  the  question  whether  i  was  a  medium,  the  response  was 
three  brisk  and  vigorous  knocks.  I  noticed  that  the 
knocks  issued  from  a  particular  locality,  and  therefore 
requested  the  spirits  to  be  good  enough  to  answer  from 


318  FRAGMENTS   OF  SCIENCE. 

another  corner  of  the  table.  They  did  not  comply  ;  but 
I  was  assured  that  they  would  do  it,  and  much  more,  by- 
and-by.  The  knocks  continuing,  I  turned  a  wine-glass 
upside  down,  and  placed  my  ear  upon  it,  as  upon  a  stetho- 
scope. The  spirits  seemed  disconcerted  by  the  act ;  they 
lost  their  playfulness,  and  did  not  quite  recover  it  for  a 
considerable  time. 

Somewhat  weary  of  the  proceedings,  I  once  threw 
myself  back  against  my  chair  and  gazed  listlessly  out  of 
the  window.  While  thus  engaged,  the  table  was  rudely 
pushed.  Attention  was  drawn  to  the  wine,  still  oscillat- 
ing in  the  glasses,  and  I  was  asked  whether  that  was  not 
convincing.  I  readily  granted  the  fact  of  motion,  and 
began  to  feel  the  delicacy  of  my  position.  There  were 
several  pairs  of  arms  upon  the  table,  and  several  pairs  of 
legs  under  it ;  but  how  was  I,  without  offence,  to  express 
the  conviction  which  I  really  entertained  ?  To  ward  off 
the  difficulty,  I  again  turned  a  wine-glass  upside  down 
and  rested  my  ear  upon  it.  The  rim  of  the  glass  was 
not  level,  and  the  hair,  on  touching  it,  caused  it  to 
vibrate,  and  produce  a  peculiar  buzzing  sound.  A  per- 
fectly candid  and  warm-hearted  old  gentleman  at  the 
opposite  side  of  the  table,  whom  I  may  call  A.,  drew 
attention  to  the  sound,  and  expressed  his  entire  belief 
that  it  was  spiritual.  I,  however,  informed  him  that  it 
was  the  moving  hair  acting  on  the  glass.  The  explana- 
tion was  not  well  received ;  and  X.,  in  a  tone  of  severe 
pleasantry,  demanded  whether  it  was  the  hair  that  had 
moved  the  table.  The  promptness  of  my  negative  pro- 
bably satisfied  him  that  my  notion  was  a  very  different 
one. 

The  superhuman  power  of  the  spirits  was  next  dwelt 
upon.  The  strength  of  man,  it  was  stated,  was  unavail- 
ing in  opposition  to  theirs.  No  human  power  could  pre- 
vent the  table  from  moving  when  they  pulled  it.  During 


SCIENCE   AND  THE   'SPIRITS.'  3J9 

the  evening  this  pulling  of  the  table  occurred,  or  rather 
was  attempted,  three  times.  Twice  the  table  moved 
when  my  attention  was  withdrawn  from  it ;  on  a  third 
occasion,  I  tried  whether  the  act  could  be  provoked  by  an 
assumed  air  of  inattention.  Grasping  the  table  firmly 
between  my  Knees,  I  threw  myself  back  in  the  chair,  and 
waited,  with  eyes  fixed  on  vacancy,  for  the  pull.  It  came. 
For  some  seconds  it  was  pull  spirit,  hold  muscle ;  the 
muscle,  however,  prevailed,  and  the  table  remained  at 
rest.  Up  to  the  present  moment,  this  interesting  fact 
is  known  only  to  the  particular  spirit  in  question  and 
myself. 

A  species  of  mental  scene-painting,  with  which  my 
own  pursuits  had  long  rendered  me  familiar,  was  employed 
to  figure  the  changes  and  distribution  of  spiritual  power. 
The  spirits  were  provided  with  atmospheres,  which  com- 
bined with  and  interpenetrated  each  other,  considerable 
ingemiity  being  shown  in  demonstrating  the  necessity  of 
time  in  effecting  the  adjustment  of  the  atmospheres.  In 
fact,  just  as  in  science,  the  senses,  time,  and  space  consti- 
tuted the  conditions  of  the  phenomena.  A  rearrangement 
of  our  positions  was  proposed  and  carried  out ;  and  soon 
afterwards  my  attention  was  drawn  to  a  scarcely  sensible 
vibration  on  the  part  of  the  table.  Several  persons  were 
leaning  on  the  table  at  the  time,  and  I  asked  permission 
to  touch  the  medium's  hand.  <  Oh  I  I  know  I  tremble,' 
was  her  reply.  Throwing  one  leg  across  the  other,  I 
accidentally  nipped  a  muscle,  and  produced  thereby  an 
involuntary  vibration  of  the  free  leg.  This  vibration,  I 
knew,  must  be  communicated  to  the  floor,  and  thence  to 
the  chairs  of  all  present.  I  therefore  intentionally  pro- 
moted it.  My  attention  was  promptly  drawn  to  the  mo- 
tion ;  and  a  gentleman  beside  me,  whose  value  as  a  witness 
I  was  particularly  desirous  to  test,  expressed  his  belief 
that  it  was  out  of  the  compass  of  human  power  to  produce 


820  FRAGMENTS   OF   SCIENCE. 

so  strange  a  tremor.  'I  believe,'  he  added,  earnestly. 
1  that  it  is  entirely  the  spirits'  work.'  '  So  do  I,'  added, 
with  heat,  the  candid  and  warmhearted  old  gentleman  A. 
'  Why,  sir,'  he  continued,  '  I  feel  them  at  this  moment 
shaking  my  chair.'  I  stopped  the  motion  of  the  leg. 
'  Now,  sir,'  A.  exclaimed,  '  they  are  gone.'  I  began  again, 
and  A.  once  more  ejaculated.  I  could,  however,  notice 
that  there  were  doubters  present,  who  did  not  quite  know 
what  to  think  of  the  manifestations.  I  saw  their  per- 
plexity ;  and,  as  there  was  sufficient  reason  to  believe  that 
the  disclosure  of  the  secret  would  simply  provoke  anger, 
I  kept  it  to  myself. 

Again  a  period  of  conversation  intervened,  during 
which  the  spirits  became  animated.  The  evening  was 
confessedly  a  dull  one,  but  matters  appeared  to  brighten 
towards  its  close.  The  spirits  were  requested  to  spell  the 
name  by  which  I  am  known  in  the  heavenly  world.  Our 
host  commenced  repeating  the  alphabet,  and  when  he 
reached  the  letter  <P'  a  knock  was  heard.  He  began 
again,  and  the  spirits  knocked  at  the  letter  '  0.'  I  was 
puzzled,  but  waited  for  the  end.  The  next  letter  knocked 
down  was  '  E.'  I  laughed,  and  remarked  that  the  spirits 
were  going  to  make  a  poet  of  me.  Admonished  for  my 
levity,  I  was  informed  that  the  frame  of  mind  proper  for 
the  occasion  ought  to  have  been  superinduced  by  a  perusal 
of  the  Bible  immediately  before  the  seance.  The  spelling, 
however,  went  on,  and  sure  enough  I  came  out  a  poet. 
But  matters  did  not  end  here.  Our  host  continued  his 
repetition  of  the  alphabet,  and  the  next  letter  of  the  name 
proved  to  be  '  0.'  Here  was  manifestly  an  unfinished 
word ;  and  the  spirits  were  apparently  in  their  most  com- 
municative mood.  The  knocks  came  from  under  the 
table,  but  no  person  present  evinced  the  slightest  desire 
to  look  under  it.  I  asked  whether  I  might  go  under- 
neath ;  the  permission  was  granted ;  so  I  crept  under  the 


SCIENCE   AND   THE   'SPIRITS.'  321 

table.  Some  tittered ;  but  the  candid  old  A.  exclaimed, 
'  He  has  a  right  to  look  into  the  very  dregs  of  it,  to  con- 
vince himself.'  Having  pretty  well  assured  myself  that 
no  sound  could  be  produced  under  the  table  without  its 
origin  being  revealed,  I  requested  our  host  to  continue  his 
questions.  He  did  so,  but  in  vain.  He  adopted  a  tone 
of  tender  entreaty;  but  the  'dear  spirits'  had  become 
dumb  dogs,  and  refused  to  be  entreated.  I  continued 
under  that  table  for  at  least  a  quarter  of  an  hour,  after 
which,  with  a  feeling  of  despair  as  regards  the  prospects 
of  humanity  never  before  experienced,  I  regained  my  chair. 
Once  there,  the  spirits  resumed  their  loquacity,  and 
dubbed  me  '  Poet  of  Science.' 

This,  then,  is  the  result  of  an  attempt  made  by  a 
scientific  man  to  look  into  these  spiritual  phenomena.  It 
is  not  encouraging ;  and  for  this  reason :  The  present 
promoters  of  spiritual  phenomena  divide  themselves  into 
two  classes,  one  of  which  needs  no  demonstration,  while 
the  other  is  beyond  the  reach  of  proof.  The  victims  like 
to  believe,  and  they  do  not  like  to  be  undeceived.  Science 
is  perfectly  powerless  in  the  presence  of  this  frame  or 
mind.  It  is,  moreover,  a  state  perfectly  compatible  with 
extreme  intellectual  subtlety  and  a  capacity  for  devising 
hypotheses  which  only  require  the  hardihood  engendered 
by  strong  conviction,  or  by  callous  mendacity,  to  render 
them  impregnable.  The  logical  feebleness  of  science  is 
not  sufficiently  borne  in  mind.  It  keeps  down  the  weed 
of  superstition,  not  by  logic  but  by  slowly  rendering  the 
mental  soil  unfit  for  its  cultivation.  When  science  appeals 
to  uniform  experience,  the  spiritualist  will  retort,  '  How 
do  you  know  that  a  uniform  experience  will"  continue 
uniform  ?  You  tell  me  that  the  sun  has  risen  for  six 
thousand  years  :  that  is  no  proof  that  it  will  rise  to-mor- 
row ;  within  the  next  twelve  hours  it  may  be  puffed  out  by 
the  Almighty.'  Taking  this  ground,  a  man  may  maintain 


322  FRAGMENTS   OF   SCIENCE. 

the  story  of  *  Jack  and  the  Beanstalk '  in  the  face  of  all 
the  science  in  the  world.  You  urge,  in  vain,  that  science 
has  given  us  all  the  knowledge  of  the  universe  which  we 
now  possess,  while  spiritualism  has  added  nothing  to  that 
knowledge.  The  drugged  soul  is  beyond  the  reach  of 
reason.  It  is  in  vain  that  impostors  are  exposed,  and  the 
special  demon  cast  out.  He  has  but  slightly  to  change 
his  shape,  return  to  his  house,  and  find  it  *  empty,  swept, 
and  garnished.' 

December  10,  I860. 


PAET  II. 


INTRODUCTION. 


IN  consequence  of  their  special  character,  the  Fragments 
of  Part  II.  have  been  separated  from  the  more  purely 
scientific  ones  of  Part  L,  and  placed  together  in  the  order 
of  their  publication.  Thus  presented,  they  will,  I  think, 
make  it  plain  that,  within  the  last  two  years,  I  have  added 
no  material  iniquity  to  the  list  previously  recorded  against 
me*  I  have  gone  carefully  over  them  all  this  year  in  Swit- 
zerland, bestowing  special  attention  upon  the  one  which  has 
given  most  offence.  To  the  judgment  of  thoughtful  men 
I  now  commit  them  :  the  unthoughtful  and  the  unfair  will 
not  read  them,  though  they  will  continue  to  abuse  them. 

I  have  no  desire  to  repay  in  kind  the  hard  words  already 
thrown  at  them  and  me ;  but  a  simple  comparison  will 
make  clear  to  my  more  noisy  and  unreasonable  assailants 
how  I  regard  their  position.  To  the  nobler  Bereans  of  the 
press  and  pulpit,  who  have  honoured  me  with  their  atten- 
tion, I  do  not  now  refer.  Webster  defines  a  squatter  as  one 
who  settles  on  new  land  without  a  title.  This,  in  regard 
to  Anthropology  and  Cosmogony,  I  hold  to  have  been 
the  position  of  the  older  theologians ;  and  what  their 
heated  successors  of  to-day  denounce  as  *  a  raid  upon  Theo- 
logy,' is,  in  my  opinion,  a  perfectly  legal  and  equitable  at- 
tempt to  remove  them  from  ground  which  they  have  no 
right  to  hold. 

If  the  title  exist,  let  it  be  produced.      It  is  not  the 


326  INTRODUCTION. 

revision  of  the  text  of  Genesis  by  accomplished  scholars 
that  the  public  so  much  need,  as  to  be  informed  and 
convinced  how  far  the  text,  polished  or  unpolished,  has  a 
claim  upon  the  belief  of  intelligent  persons.  It  is,  I  fear, 
a  growing  conviction  that  our  ministers  of  religion,  for  the 
sake  of  peace,  more  or  less  sacrifice  their  sincerity  in  deal- 
ing with  the  Cosmogony  of  the  Old  Testament.  I  notice 
this  in  conversation,  and  it  is  getting  into  print.  Before 
me,  for  example,  is  a  little  brochure,  in  which  a  layman 
presses  a  clerical  friend  with  a  series  of  questions  regarding 
Creation — the  six-day  period  of  Divine  activity,  the  destruc- 
tion of  the  world  by  a  flood,  the  building  of  an  ark,  the 
placing  of  creatures  in  it  by  pairs,  and  the  descent  from 
this  ancestry  of  all  living  things,  l  men  and  women,  birds 
and  beasts.'  He  asks  his  friend,  '  Do  you  without  any 
tnental  reservation  believe  these  things  ?  '  l  If  you  do,' 
be  continues,  l  then  I  can  only  say  that  the  accumulated 
and  accepted  knowledge  of  mankind,  including  the  entire 
sciences  of  Astronomy,  Geology,  Philology,  and  History, 
are  [as  far  as  you  are  concerned]  nought  and  mistaken. 
If  you  do  not  believe  those  events  to  have  so  happened, 
or  do  so  with  some  mental  reservation,  which  destroys  the 
whole  sense  and  meaning  of  the  narrative,  why  do  you 
not  say  so  from  your  pulpits  ? ' 

The  friend  merely  parries  and  evades  the  question. 
According  to  Mr.  Martineau,  the  clergy  speak  very  differ- 
ently indeed  from  their  pulpits.  After  showing  how  the 
Mosaic  picture  of  the  l  genetic  order  of  things  '  has  been 
not  only  altered  but  inverted  by  scientific  research,  he  says : 
'  Notwithstanding  the  deplorable  condition  to  which  the 
picture  has  been  reduced,  it  is  exhibited  fresh  every  week 
to  millions  taught  to  believe  it  as  divine.'  It  cannot  be 
urged  that  error  here  does  no  practical  harm,  or  that  it 
does  not  act  to  the  detriment  of  honest  men.  It  was  for 
openly  avowing  doubts  which,  it  is  said,  others  discreetly 


INTKODUCTIOff.  327 

entertain,  that  the  Bishop  of  Natal  suffered  persecution; 
it  was  for  his  public  fidelity  to  scientific  truth,  as  far  as 
his  lights  extended,  that  he  was  branded,  even  during  his 
recent  visit  to  this  country,  as  an  c  excommunicated 
heretic.'  The  courage  of  Dean  Stanley  and  of  the  Master 
of  Balliol,  in  reference  to  this  question,  disarmed  indig- 
nation, and  caused  the  public  to  overlook  a  wrong  which 
might  not  otherwise  have  been  endured. 

The  liberal  and  intelligent  portion  of  Christendom 
must,  I  take  it,  differentiate  itself  more  and  more,  in  word 
and  act,  from  the  fanatical,  foolish,  and  more  purely 
sacerdotal  portion.  Enlightened  Eoman  Catholics  are 
more  especially  bound  to  take  action  here;  for  the  travesty 
of  heaven  and  earth  is  grosser,  and  the  attempt  to  impose 
it  on  the  world  is  more  serious,  in  their  community  than 
elsewhere.  That  they  are  more  or  less  alive  to  this  state 
of  things,  and  that  they  show  an  increasing  courage  and 
independence  in  their  demands  for  education,  will  be  plain 
to  the  reader  of  the  l  Apology  for  the  Belfast  Address.' 
The  '  Memorial '  there  referred  to  was  the  impatient  pro- 
test of  barristers,  physicians,  surgeons,  solicitors,  and 
scholars  among  the  Catholics  themselves.  They  must  not 
relax  their  pressure  nor  relinquish  their  demands.  For 
their  spiritual  guides  live  so  exclusively  in  the  pre-scien- 
tific  past,  that  even  the  really  strong  intellects  among 
them  are  reduced  to  atrophy  as  regards  scientific  truth. 
Eyes  they  have,  and  see  not ;  ears  they  have,  and  hear 
not ;  for  both  eyes  and  ears  are  taken  possession  of  by  the 
sights  and  sounds  of  another  age.  In  relation  to  Science, 
the  Ultramontane  brain,  through  lack  of  exercise,  is  virtu- 
ally the  undeveloped  brain  of  the  child.  And  thus  it  is  that 
as  children  in  scientific  knowledge,  but  as  potent  wielders 
of  spiritual  power  among  the  ignorant,  they  countenance 
and  enforce  practices  sufficient  to  bring  the  blush  of  shame 
to  the  cheeks  of  the  more  intelligent  among  themselves. 


828 

Such  is  the  force  of  early  education,  when  maintained 
and  perpetuated  by  the  habits  of  subsequent  life ;  such  the 
ground  of  peril  in  allowing  the  schools  of  a  nation  to  fall 
into  Ultramontane  hands.  Let  any  able  Catholic  student, 
fairly  educated,  and  not  yet  cramped  by  sacerdotalism,  get 
a  real  scientific  grasp  of  the  magnitude  and  organisation  of 
this  universe.  Let  him  sit  under  the  immeasurable  heavens, 
watch  the  stars  in  their  courses,  scan  the  mysterious  nebulae, 
and  try  to  realise  what  it  all  is  and  means.  Let  him  bring 
the  thoughts  and  conceptions  which  thus  enter  his  mind 
face  to  face  with  the  notions  of  the  genesis  and  rule  of 
things  which  pervade  the  writings  of  the  princes  of  his 
Church,  and  he  will  see  and  feel  what  drivellers  even  men 
of  strenuous  intellects  may  become,  through  exclusively 
dwelling  and  dealing  with  theological  chimeras. 

But,  quitting  the  more  grotesque  forms  of  the  Theolo- 
gical, I  already  see,  or  think  I  see,  emerging  from  recent 
discussions,  that  wonderful  plasticity  of  the  Theistic  Idea 
which  enables  it  to  maintain,  through  many  changes,  its 
hold  upon  superior  minds  ;  and  which,  if  it  is  to  last, 
will  eventually  enable  it  to  shape  itself  in  accordance  with 
scientific  conditions.  I  notice  this,  for  instance,  in  the 
philosophic  sermon  of  Dr.  Quarry,  and  more  markedly  still 
in  that  of  Dr.  Eyder.  '  There  pervades,'  says  the  Rector 
of  Donnybrook,  'these  atoms  and  that  illimitable  universe, 
that  "  choir  of  heaven  and  furniture  of  earth,"  which  of 
such  atoms  is  built  up,  a  certain  force,  known  in  its  most 
familiar  form  by  the  name  of  "  life,"  which  may  be  re- 
garded as  the  ultimate  essence  of  matter.^  And,  speaking 
of  the  awful  search  of  the  intellect  for  the  infinite  Creator, 
and  of  the  grave  difficulties  which  encompass  the  subject, 
the  same  writer  says :  i  We  know  from  our  senses  finite 
existences  only.  Now  we  cannot  logically  infer  the  ex- 
istence of  an  infinite  God  from  the  greatest  conceivable 
number  of  finite  existences.  There  must  always  obviously 


INTRODUCTION.  329 

be  more  in  the  conclusion  than  in  the  premisses.'  Such 
language  is  new  to  the  pulpit,  but  it  "will  become  less  and 
less  rare.  It  is  not  the  poets  and  philosophers  among  our 
theologians — and  in  our  day  the  philosopher  who  wanders 
beyond  the  strict  boundary  of  Science  is  more  or  less 
merged  in  the  poet — it  is  not  these,  who  feel  the  life  of 
religion,  but  the  mechanics,  who  cling  to  its  scaffolding, 
that  are  most  anxious  to  tie  the  world  down  to  the  un- 
tenable conceptions  of  an  uncultivated  past. 

Before  me  is  another  printed  sermon  of  a  different 
character  from  those  just  referred  to.  It  is  entitled 
'The  Necessary  Limits  of  Christian  Evidences.'  Its 
author,  Dr«  Eeichel,  has  been  frequently  referred  to  as  an 
authority,  particularly  on  personal  subjects,  during  recent 
discussions.  The  sermon  was  first  preached  in  Belfast, 
and  afterwards,  in  an  amplified  and  amended  form,  in 
the  Exhibition  Building  in  Dublin.  In  passing,  I  would 
make  a  single  remark  upon  its  opening  paragraph.  This 
contains  an  argument  regarding  Christ  which  I  have  fre- 
quently heard  used  in  substance  by  good  men,  though  never 
before  with  the  grating  emphasis  here  employed.  '  The  re- 
surrection of  our  Saviour,'  says  Dr.  Eeichel, '  is  the  central 
fact  of  Christianity.  Without  His  resurrection,  His  birth 
and  His  death  would  have  been  alike  unavailing ;  nay 
more,  if  He  did  not  rise  from  the  dead,  His  birth  was  the 
birth  of  a  bastard,  and  His  death  the  death  of  an  impostor.' 
This  may  be  '  orthodoxy ; '  but  entertaining  the  notions 
that  I  do  of  Christ,  and  of  His  incomparable  life  upon  the 
earth,  if  the  momentary  use  of  the  term  '  blasphemy ' 
were  granted  to  me  by  my  Christian  brethren,  I  should 
feel  inclined  to  employ  it  here. 

Better  instructed  than  he  had  been  at  Belfast,  the 
orator  in  Dublin  gave  prominence  to  a  personal  argu- 
ment which  I  have  noticed  elsewhere.1  He  has  been 
1  '  Apology  for  Belfast  Address.' 


330  INTRODUCTION. 

followed  in  this  particular  by  the  Bishop  of  Meath  and 
other  estimable  persons.  This  is  to  be  regretted,  be- 
cause in  dealing  with  these  high  themes  the  mind  ought 
to  be  the  seat  of  dignity — if  possible  of  chivalry — but 
certainly  not  the  seat  of  littleness.  '  I  propose,'  says 
the  preacher,  '  making  some  remarks  on  the  doctrine 
thus  propounded  [in  Belfast].  And,  first,  lest  any  of 
you  should  be  unduly  impressed  by  the  mere  authority 
of  its  propounder,  as  well  as  by  the  fluent  grace  with 
which  he  sets  it  forth,  it  is  right  that  I  should  tell 
you,  that  these  conclusions,  though  given  out  on  an  occa- 
sion which  apparently  stamped  them  with  the  general 
approbation  of  the  scientific  world,  do  not  possess  that 
approbation.  The  mind  that  arrived  at  them,  and  dis- 
played them  with  so  much  complacency,  is  a  mind  trained 
in  the  school  of  mere  experiment,  not  in  the  study,  but 
in  the  laboratory.  Accordingly  the  highest  mathematical 
intellects  of  the  Association  disclaim  and  repudiate  the 
theories  of  its  President.  In  the  mathematical  laws  to 
which  all  material  phenomena  and  substances  are  each 
year  more  distinctly  perceived  to  be  subordinated,  they 
see  another  side  of  Nature,  which  has  not  impressed  itself 
upon  the  mere  experimentalist.'  * 

In  view  of  the  new  virtue  here  thrust  upon  the 
mathematician,  D'Alembert  and  Laplace  present  a  diffi- 
culty, and  we  are  left  without  a  clue  to  the  peculiar 
orthodoxy  of  Helmholtz,  Clifford,  and  other  distinguished 
men.  As  regards  my  own  mental  training,  inasmuch 
as  my  censors  think  it  not  beneath  them  to  dwell 
upon  a  point  so  small,  I  may  say  that  the  foregoing 
statement  is  incorrect.  The  separation,  moreover,  of  the 
'study'  from  the  'laboratory'  is  not  admissible,  because 

1  «Es  ist  ihre  Taktik,  die  Gegner,  gegen  welche  sie  nichts  sonst 
auszurichten  vermogen,  verachtlich  zu  behandeln,  und  aUmahlich  in  der 
Achtung  des  Publikums  herabzusetzen.'  This  -was  written  of  the  Jesuits  in 
reference  to  their  treatment  of  Dr.  Dollinger.  It  is  true  of  others. 


INTRODUCTION.  331 

the  laboratory  is  a  '  study '  in  which  symbols  give  place 
to  natural  facts.  The  word  Mesopotamia  is  said  to  have  a 
sacred  unction  for  many  minds,  and  possibly  the  title  of 
my  *  Inaugural  Dissertation '  at  Marburg  may  have  an  effect 
of  this  kind  on  my  right  reverend  and  reverend  critics  of 
the  new  mathematical  school.  Here  accordingly  it  is: 
'  Die  Schraubenflache  mit  geneigter  Erzeugungslinie, 
und  die  Bedingungen  des  Grleichgewichts  auf  solchen 
Schrauben.'  A  little  tenderness  may,  perhaps,  flow 
towards  me,  after  these  words  have  made  it  known  that 
I  began  my  narrow  scientific  life  less  as  an  experimentalist 
than  as  a  mathematician. 

If,  as  asserted,  'the  highest  mathematical  intellects  of 
the  Association  disclaim  and  repudiate  the  theories  of  its 
President,'  it  would  be  their  bounden  duty  not  to  rest  con- 
tent with  this  mere  second-hand  utterance.  They  ought 
to  permit  the  light  of  life  to  stream  upon  us  directly  from 
themselves,  instead  of  sending  it  through  the  rude  pole- 
moscope1  of  Dr.  Keichel.  But  the  point  of  importance 
to  be  impressed  upon  him,  and  upon  those  who  may  be 
tempted  to  follow  him  in  his  adventurous  theories,  is, 
that  out  of  Mathematics  no  salvation  for  Theology  can 
possibly  come. 

By  such  reflections  I  am  brought  face  to  face  with  an 
essay  to  which  my  attention  has  been  directed  by  several 
estimable,  and  indeed  eminent,  persons,  as  demanding 
serious  consideration  at  my  hands.  I  refer  with  pleasure 
to  the  accord  subsisting  between  the  Eev.  James  Marti- 
neau  and  myself  on  certain  points  of  biblical  Cos- 
mogony. '  In  so  far,'  says  Mr.  Martineau,  '  as  Church  be- 
lief is  still  committed  to  a  given  Cosmogony  and  natural 

1  'An  oblique  perspective  glass,  for  seeing  objects  not  directly  before 
the  eyes.' — Webster.  To  mere  obliquity,  Dr.  Keichel's  instrument  adds 
coarseness  of  construction. 


332  INTRODUCTION. 

history  of  man,  it  lies  open  to  scientific  refutation.'  And 
again  :  *  It  turns  out  that  with  the  sun  and  moon  and  stars, 
and  in  and  on  the  earth,  before  and  after  the  appearance  of 
our  race,  quite  other  things  have  happened  than  those  which 
the  sacred  Cosmogony  recites.'  Once  more :  *  The  whole 
history  of  the  genesis  of  things  Eeligion  must  sur- 
render to  the  Sciences.'  Finally,  still  more  emphatically  : 
4  In  the  investigation  of  the  genetic  order  of  things, 
Theology  is  an  intruder,  and  must  stand  aside.'  This 
expresses,  only  in  words  of  fuller  pith,  the  views  which  I 
ventured  to  enunciate  in  Belfast.  *  The  impregnable 
position  of  Science,'  I  there  say,  '  may  be  stated  in  a  few 
words.  We  claim,  and  we  shall  wrest  from  Theology,  the 
entire  domain  of  Cosmological  theory.'  Thus  Theology, 
so  far  as  it  is  represented  by  Mr.  Martineau,  and  Science, 
so  far  as  I  understand  it,  are  in  absolute  harmony  here. 

But  Mr.  Martineau  would  have  just  reason  to  com- 
plain of  me,  if,  by  partial  citation,  I  left  my  readers 
under  the  impression  that  the  agreement  between  us  is 
complete.  At  the  opening  of  the  eighty-ninth  Session 
of  the  Manchester  New  College,  London,  on  October  6, 
1874,  he,  its  principal,  delivered  the  Address  from  which  I 
have  quoted.  It  bears  the  title  *  Eeligion  as  affected  by 
Modern  Materialism ; '  and  its  references  and  general  tone 
make  evident  the  depth  of  its  author's  discontent  with 
my  previous  deliverance  at  Belfast.  I  find  it  difficult  to 
grapple  with  the  exact  grounds  of  this  discontent.  In- 
deed, logically  considered,  the  impression  left  upon  my 
mind  by  an  essay  of  great  aesthetic  merit,  containing  many 
passages  of  exceeding  beauty,  and  many  sentiments  which 
none  but  the  pure  in  heart  could  utter  as  they  are  uttered 
here,  is  vague  and  unsatisfactory.  The  author  appears 
at  times  so  brave  and  liberal,  at  times  so  timid  and 
captious,  and  at  times  so  imperfectly  informed  regarding 
the  position  he  assails. 


INTRODUCTION.  333 

At  the  outset  of  his  Address  Mr.  Martineau  states  with 
some  distinctness  his  '  sources  of  religious  faith.'  They 
are  two — *  the  scrutiny  of  Nature '  and  '  the  interpretation 
of  Sacred  Books.'  It  would  have  been  a  theme  worthy  of 
his  intelligence  to  have  deduced  from  these  two  sources 
his  religion  as  it  stands.  But  not  another  word  is  said 
ahout  the  *  Sacred  Books.'  Having  swept  with  the  besom 
of  Science  various  '  books  '  contemptuously  away,  he  does 
not  define  the  Sacred  residue ;  much  less  give  us  the 
reasons  why  he  deems  them  sacred.  His  references  to 
*  Nature,'  on  the  other  hand,  are  magnificent  tirades 
against  Nature,  intended,  apparently,  to  show  the  wholly 
abominable  character  of  man's  antecedents  if  the  theory 
of  evolution  be  true.  Here  also  his  mood  lacks  steadiness. 
While  joyfully  accepting,  at  one  place, '  the  widening  space, 
the  deepening  vistas  of  time,  the  detected  marvels  of  physio- 
logical structure,  and  the  rapid  filling-in  of  the  missing  links 
in  the  chain  of  organic  life,'  he  falls,  at  another,  into  lament- 
ation and  mourning  over  the  very  theory  which  renders 
'  organic  life '  *  a  chain.'  He  claims  the  largest  liberality  for 
his  sect,  and  avows  its  contempt  for  the  dangers  of  possible 
discovery.  But  immediately  afterwards  he  damages  the 
claim,  and  ruins  all  confidence  in  the  avowal.  He  professes 
sympathy  with  modern  Science,  and  almost  in  the  same 
breath  he  treats,  or  certainly  will  be  understood  to  treat, 
the  Atomic  Theory,  and  the  doctrine  of  the  Conservation 
of  Energy,  as  if  they  were  a  kind  of  scientific  thimble- 
riggery. 

His  ardour,  moreover,  renders  him  inaccurate  ;  causing 
him  to  see  discord  between  scientific  men,  where  nothing 
but  harmony  reigns.  In  his  celebrated  Address  to  the 
Congress  of  German  Naturforscher,  delivered  at  Leipzig, 
three  years  ago,  Du  Bois  Eeymond  speaks  thus  :  '  What 
conceivable  connection  subsists  between  definite  move- 
ments of  definite  atoms  in  my  brain,  on  the  one  hand, 


834  INTRODUCTION. 

and  on  the  other  hand  such  primordial,  indefinable,  un- 
deniable, facts  as  these  :  I  feel  pain  or  pleasure  ;  I  ex- 
perience a  sweet  taste,  or  smell  a  rose,  or  hear  an  organ, 
or  see  something  red.  ...  It  is  absolutely  and  for  ever 
inconceivable  that  a  number  of  carbon,  hydrogen,  nitro- 
gen, and  oxygen  atoms  should  be  otherwise  than  indif- 
ferent as  to  their  own  position  and  motion,  past,  present, 
or  future.  It  is  utterly  inconceivable  how  consciousness 
should  result  from  their  joint  action.' 

This  language,  which  was  spoken  in  1872,  Mr.  Mar- 
tineau  '  freely  '  translates,  and  quotes  against  me.  The 
act  is  due  to  a  misapprehension  of  his  own.  Evidence  is 
at  hand  to  prove  that  I  employed  the  same  language 
twenty  years  ago.  It  is  to  be  found  in  the  '  Saturday 
Keview'  for  1860;  but  a  sufficient  illustration  of  the  agree- 
ment between  my  friend  Du  Bois  Eeymond  and  myself, 
is  furnished  by  the  discourse  on  <  Scientific  Materialism,' 
delivered  in  1868,  then  widely  circulated,  and  reprinted 
here.  With  a  little  attention,  Mr.  Martineau  would 
have  seen  that  in  the  very  Address  his  essay  criticises, 
precisely  the  same  position  is  maintained.  'You  can- 
not,' I  there  say,  c  satisfy  the  human  understanding  in 
its  demand  for  logical  continuity  between  molecular  pro- 
cesses and  the  phenomena  of  consciousness.  This  is  a 
rock  on  which  materialism  must  inevitably  split  when- 
ever it  pretends  to  be  a  complete  philosophy  of  the  human 
mind.' 

1  The  affluence  of  illustration,'  writes  an  able  and  sym- 
pathetic reviewer  of  this  essay,  in  the  l  New  York  Tribune,' 
'in  which  Mr. Martineau  delights  often  impairs  the  distinct- 
ness of  his  statements  by  diverting  the  attention  of  the 
reader  from  the  essential  points  of  his  discussion  to  the 
beauty  of  his  imagery,  and  thus  diminishes  their  power  of 
conviction.'  To  the  beauties  here  referred  to  I  bear  willing 


INTRODUCTION.  886 

testimony  ;  but  the  excesses  touched  upon  reach  far  be- 
yond the  reader,  to  their  primal  seat  and  source  in  Mr. 
Martineau's  own  mind ;  mixing  together  there  things 
that  ought  to  be  kept  apart ;  producing  vagueness  where 
precision  is  the  one  thing  needful ;  poetic  fervour  where 
we  require  judicial  calm ;  and  practical  unfairness  where 
the  strictest  justice  ought  to  be,  and  I  willingly  believe  is 
meant  to  be,  observed. 

In  one  of  his  nobler  passages  Mr.  Martineau  tells  us 
how  the  pupils  of  his  college  have  been  educated  hitherto : 
'  They  have  been  trained  under  the  assumptions  (1st)  that 
the  Universe  which  includes  us  and  folds  us  round  is  the 
life-dwelling  of  an  Eternal  Mind  ;  (2nd)  that  the  world  of 
our  abode  is  the  scene  of  a  moral  government,  incipient 
but  not  complete;  and  (3rd)  that  the  upper  zones  of 
human  affection,  above  the  clouds  of  self  and  passion, 
take  us  into  the  sphere  of  a  Divine  Communion.  Into 
this  over-arching  scene  it  is  that  growing  thought  and 
enthusiasm  have  expanded  to  catch  their  light  and  fire.' 

Alpine  summits  must  kindle  above  the  mountaineer 
who  reads  these  stirring  words  ;  I  see  their  beauty  and  feel 
their  life.  Nay,  in  my  own  feeble  way,  at  the  close  of  one  of 
the  essays  here  printed,  I  thus  affirm  the  '  Communion ' 
which  Mr.  Martineau  calls  '  Divine':  ' "  Two  things,"  said 
Immanuel  Kant,  "fill  me  with  awe — the  starry  heavens, and 
the  sense  of  moral  responsibility  in  man."  And  in  his  hours 
of  health  and  strength  and  sanity,  when  the  stroke  of  action 
has  ceased,  and  the  pause  of  reflection  has  set  in,  the  scien- 
tific investigator  finds  himself  overshadowed  by  the  same 
awe.  Breaking  contact  with  the  hampering  details  of  earth, 
it  associates  him  with  a  power  which  gives  fulness  and  tone 
to  his  existence,  but  which  he  can  neither  analyse  nor 
comprehend.' l 

1  In  the  first  Preface  to  the  '  Belfast  Address '  I  referred  to  '  hours  oi 


836  INTRODUCTION. 

Though  '  knowledge'  is  here  disavowed,  the  '  feelings' 
of  Mr.  Martineau  and  myself  are,  I  think,  very  much  alike. 
But,  notwithstanding  the  mutual  independence  of  religious 
feeling  and  objective  knowledge  thus  demonstrated,  he  cen- 
sures me — almost  denounces  me — for  referring  Religion  to 
the  region  of  Emotion.  Surely  he  is  inconsistent  here. 
The  foregoing  words  refer  to  an  inward  hue  or  tempera- 
ture, rather  than  to  an  external  object  of  thought.  When 
I  attempt  to  give  the  Power  which  I  see  manifested  in 
the  Universe  an  objective  form,  personal  or  otherwise,  it 
slips  away  from  me,  declining  all  intellectual  manipula- 
tion. I  dare  not,  save  poetically,  use  the  pronoun  '  He ' 
regarding  it ;  I  dare  not  call  it  a  '  Mind  ; '  I  refuse  to 
call  it  even  a  '  Cause.'  Its  mystery  overshadows  me ; 
but  it  remains  a  mystery,  while  the  objective  frames 
which  my  neighbours  try  to  make  it  fit,  simply  distort 
and  desecrate  it. 

It  is  otherwise  with  Mr.  Martineau,  and  hence  his 
discontent.  He  professes  to  know  where  I  only  claim 
to  feel.  He  could  make  his  contention  good  against  me 
if  he  would  transform,  by  a  process  of  verification,  the 
foregoing  three  assumptions  into  'objective  knowledge.' 
But  he  makes  no  attempt  to  do  so.  They  remain 
assumptions  from  the  beginning  of  his  Address  to  its  end. 
And  yet  he  frequently  uses  the  word  '  unverified,'  as  if  it 
were  fatal  to  the  position  on  which  its  incidence  falls.  '  The 
scrutiny  of  Nature '  is  one  of  his  sources  of  '  religious 
faith  : '  what  logical  foothold  does  that  scrutiny  furnish 
on  which  any  one  of  the  foregoing  three  assumptions 

clearness  and  vigour'  as  four  years  previously  I  had  referred  to  hours  of 
'  health  and  strength  and  sanity ; '  and  brought  down  upon  myself,  in  conse- 
quence, a  considerable  amount  of  ridicule.  Why,  I  know  not.  For  surely  it  is 
not  when  sleepy  after  a  gluttonous  meal,  or  when  suffering  from  dyspepsia, 
or  even  when  possessed  by  an  arithmetical  problem  demanding  concentrated 
thought,  that  we  care  most  for  the  '  starry  heavens  or  the  sense  of  respon- 
ndbility  in  man.' 


INTRODUCTION.  337 

could  be  planted  ?  Nature,  according  to  his  picturing,  is 
base  and  cruel :  what  is  the  inference  to  be  drawn  regard- 
ing its  Author  ?  If  Nature  be  « red  in  tooth  and  claw,' 
who  is  responsible  ?  On  a  Mindless  nature  Mr.  Martineau 
pours  the  full  torrent  of  his  gorgeous  invective  ;  but  could 
the  '  assumption '  of  '  an  Eternal  Mind ' — even  of  a  Bene- 
ficent Eternal  Mind — render  the  world  objectively  a  whit 
less  mean  and  ugly  than  it  is  ?  Not  an  iota.  It  is  man's 
feelings,  and  not  external  phenomena,  that  are  influenced 
by  the  assumption.  It  adds  not  a  ray  of  light  nor  a 
strain  of  music  to  the  objective  sum  of  things.  It  does 
not  touch  the  phenomena  of  physical  nature — storm,  flood, 
or  fire — nor  diminish  by  a  pang  the  bloody  combats  of 
the  animal  world.  But  it  does  add  the  glow  of  reli- 
gious emotion  to  the  human  soul,  as  represented  by  Mr. 
Martineau.  Beyond  this  I  defy  him  to  go ;  and  yet 
he  rashly — it  might  be  said  petulantly — kicks  away  the 
only  philosophic  foundation  on  which  it  is  possible  for  him 
to  build  his  religion. 

He  twits  incidentally  the  modern  scientific  interpreta- 
tion of  nature  because  of  its  want  of  cheerfulness.  '  Let 
the  new  future,'  he  says,  '  preach  its  own  gospel,  and 
devise,  if  it  can,  the  means  of  making  the  tidings  glad.1 
This  is  a  common  argument :  *  If  you  only  knew  the 
comfort  of  belief ! '  My  reply  to  it  is  that  I  choose  the 
nobler  part  of  Emerson,  when,  after  various  disenchant - 
ments,  he  exclaimed,  '  I  covet  truth ! '  The  gladness  of 
true  heroism  visits  the  heart  of  him  who  is  really  compe- 
tent to  say  this.  Besides,  '  gladness '  is  an  emotion,  and 
Mr.  Martineau  theoretically  scorns  the  emotional.  I  am 
not,  however,  acquainted  with  a  writer  who  draws  more 
largely  upon  this  source,  while  mistaking  it  for  something 
objective.  '  To  reach  the  Cause,'  he  says,  '  there  is  no  need 
to  go  into  the  past,  as  though  being  missed  here  He  could 
be  found  there.  But  when  once  He  has  been  appre- 


338  INTRODUCTION. 

bended  by  the  proper  organs  of  divine  apprehension, 
the  whole  life  of  Humanity  is  recognised  as  the  scene  of 
His  agency.'  That  Mr.  Martineau  should  have  lived  so 
long,  thought  so  much,  and  failed  to  recognise  the  en- 
tirely subjective  character  of  this  creed,  is  highly  in- 
structive. His  '  proper  organs  of  divine  apprehension ' 
— denied,  I  may  say,  to  some  of  the  greatest  intellects 
and  noblest  men  in  this  and  other  ages — lie  at  the  very 
core  of  his  emotions. 

In  fact,  it  is  when  Mr.  Martineau  is  most  purely  emo- 
tional that  he  scorns  the  emotions;  and  it  is  when  he  is  most 
purely  subjective  that  he  rejects  subjectivity.  He  pays  a 
just  and  liberal  tribute  to  the  character  of  John  Stuart 
Mill.  But  in  the  light  of  Mill's  philosophy,  benevolence, 
honour,  purity,  having  '  shrunk  into  mere  unaccredited 
subjective  susceptibilities,  have  lost  all  support  from 
Omniscient  approval,  and  all  presumable  accordance  with 
the  reality  of  things.'  If  Mr.  Martineau  had  given  them 
any  inkling  of  the  process  by  which  he  renders  the  '  sub- 
jective susceptibilities'  objective,  or  how  he  arrives  at 
an  objective  ground  of  '  Omniscient  approval,'  grati- 
tude from  his  pupils  would  have  been  his  just  meed. 
But,  as  it  is,  he  leaves  them  lost  in  an  iridescent  cloud  of 
words,  after  exciting  a  desire  which  he  is  incompetent  to 
appease. 

'  We  are,'  he  says,  in  another  place,  '  for  ever  shaping 
our  representations  of  invisible  things  into  forms  of  de- 
finite opinion,  and  throwing  them  to  the  front,  as  if 
they  were  the  photographic  equivalent  of  our  real  faith. 
It  is  a  delusion  which  affects  us  all.  Yet  somehow  the 
essence  of  our  religion  never  finds  its  way  into  these 
frames  of  theory :  as  we  put  them  together  it  slips  away, 
and,  if  we  turn  to  pursue  it,  still  retreats  behind  ;  ever 
ready  to  work  with  the  will,  to  unbind  and  sweeten  the 
affections,  and  bathe  the  life  with  reverence,  but  refusing 


INTRODUCTION.  339 

lo  be  seen,  or  to  pass  from  a  divine  hue  of  thinking  into 
a  human  pattern  of  thought.'  This  is  very  beautiful,  and 
mainly  so  because  the  man  who  utters  it  obviously 
brings  it  all  out  of  the  treasury  of  his  own  heart.  But 
the  '  hue '  and  '  pattern '  here  so  finely  spoken  of,  are 
neither  more  nor  less  than  that  'emotion,'  on  the  one 
hand,  and  that  '  objective  knowledge,'  on  the  other, 
which  have  drawn  this  suicidal  fire  from  Mr.  Martineau's 
battery. 

I  now  come  to  one  of  the  most  serious  portions  of 
Mr.  Martineau's  pamphlet — serious  far  less  on  account  of 
its  '  personal  errors,'  than  of  its  intrinsic  gravity,  though 
its  author  has  thought  fit  to  give  it  a  witty  and  sarcastic 
tone.  He  analyses  and  criticises  '  the  materialist 
doctrine,  which,  in  our  time,  is  proclaimed  with  so  much 
pomp,  and  resisted  with  so  much  passion.  "  Matter  is  all 
I  want,"  says  the  physicist ;  "  give  me  its  atoms  alone,  and 
I  will  explain  the  universe." '  It  is  thought,  even  by  Mr. 
Martineau's  intimate  friends,  that  in  this  pamphlet  he  is 
answering  me.  I  must  therefore  ask  the  reader  to  con- 
trast the  foregoing  travesty  with  what  I  really  do  say 
regarding  atoms :  '  I  do  not  think  that  he  [the  material- 
ist] is  entitled  to  say  that  his  molecular  groupings  and 
motions  explain  everything.  In  reality,  they  explain 
nothing.  The  utmost  he  can  affirm  is  the  association  of 
two  classes  of  phenomena,  of  whose  real  bond  of  union  he 
is  in  absolute  ignorance.' l  This  is  very  different  from 
saying,  '  Give  me  its  atoms  alone,  and  I  will  explain  the 
universe.'  Mr.  Martineau  continues  his  dialogue  with  the 
physicist :  ' "  Good,"  he  says ;  "  take  as  many  atoms  as 
you  please.  See  that  they  have  all  that  is  requisite  to  Body 
[a  metaphysical  B],  being  homogeneous  extended  solids." 
"  That  is  not  enough,"  he  replies ;  "  it  might  do  for 

1  Address  on  '  Scientific  Materialism.' 

17 


840  INTEODUCTIOX. 

Democritus  and  the  mathematicians,  but  I  must  have 
something  more.  The  atoms  must  not  only  be  in  motion, 
and  of  various  shapes,  but  also  of  as  many  kinds  as  there 
are  chemical  elements  ;  for  how  could  I  ever  get  water  if 
I  had  only  hydrogen  elements  to  work  with  ?  "  "  So  be  it," 
Mr.  Martineau  consents  to  reply,  "  only  this  is  a  consider- 
able enlargement  of  your  specified  datum  [where,  and 
by  whom  specified  ?] — in  fact,  a  conversion  of  it  into 
several ;  yet,  even  at  the  cost  of  its  monism  [put  into  it 
by  Mr.  Martineau]  your  scheme  seems  hardly  to  gain 
its  end;  for  by  what  manipulation  of  your  resources 
will  you,  for  example,  educe  Consciousness  ?  "  * 

This  reads  like  pleasantry,  but  it  deals  with  serious 
things.  For  the  last  seven  years  the  question  proposed 
by  Mr.  Martineau  and  my  answer  to  it  have  been  access- 
ible to  all.  They  are  also  given  in  this  volume.  Here, 
briefly,  is  the  question :  c  A  man  can  say,  "  I  feel,  I 
think,  I  love,"  but  how  does  consciousness  infuse  itself  into 
the  problem  ? '  And  here  is  the  answer :  '  The  passage 
from  the  physics  of  the  brain  to  the  corresponding  facts 
of  consciousness  is  unthinkable.  Granted  that  a  definite 
thought  and  a  definite  molecular  action  in  the  brain 
occur  simultaneously ;  we  do  not  possess  the  intellectual 
organ,  nor  apparently  any  rudiment  of  the  organ,  which 
would  enable  us  to  pass,  by  a  process  of  reasoning,  from 
the  one  to  the  other.  They  appear  together,  but  we  do 
not  know  why.  Were  our  minds  and  senses  so  expanded, 
strengthened,  and  illuminated,  as  to  enable  us  to  see  and 
feel  the  very  molecules  of  the  brain  ;  were  we  capable  of  fol- 
lowing all  their  motions,  all  their  groupings,  all  their 
electric  discharges,  if  such  there  be ;  and  were  we  inti- 
mately acquainted  with  the  corresponding  states  of  thought 
and  feeling,  we  should  be  as  far  as  ever  from  the  solution 
of  the  problem,  "  How  are  these  physical  processes  con- 
nected with  the  facts  of  consciousness  ? "  The  chasm 


INTRODUCTION.  841 

between  the  two  classes  of  phenomena  would  still  remain 
intellectually  impassable.' ' 

Compare  this  with  the  answer  which  Mr.  Martineau 
puts  into  the  mouth  of  his  physicist,  and  with  which  I  am 
generally  credited  by  Mr.  Martineau's  readers :  '  "  It  [the 
problem  of  consciousness]  does  not  daunt  me  at  all.  Of 
course  you  understand  that  all  along  my  atoms  have  been 
affected  by  gravitation  and  polarity;  and  now  I  have  only 
to  insist  with  Fechner  on  a  difference  among  molecules : 
there  are  the  inorganic,  which  can  change  only  their 
place,  like  the  particles  in  an  undulation  ;  and  there  are 
the  organic,  which  can  change  their  order,  as  in  a  globule 
that  turns  itself  inside  out.  With  an  adequate  number 
of  these,  our  problem  will  be  manageable."  "  Likely 
enough,"  we  may  say  ["  entirely  unlikely,"  say  I],  "  seeing 
how  careful  you  are  to  provide  for  all  emergencies  ;  and 
if  any  hitch  should  occur  in  the  next  step,  where  you  will 
have  to  pass  from  mere  sentiency  to  thought  and  will,  you 
can  again  look  in  upon  your  atoms,  and  fling  among  them 
a  handful  of  Leibnitz's  monads,  to  serve  as  souls  in  little, 
and  be  ready,  in  a  latent  form,  with  that  Vorstellungs- 
fahigkeit  which  our  picturesque  interpreters  of  nature  so 
much  prize." ' 

4  But  surely,'  continues  Mr.  Martineau,  c  you  must 
observe  that  this  "  matter  "  of  yours  alters  its  style  with 
every  change  of  service  :  starting  as  a  beggar,  with  scarce 
a  rag  of  "  property  "  to  cover  its  bones,  it  turns  up  as  a 
prince  when  large  undertakings  are  wanted.  "  We  must 
radically  change  our  notions  of  matter,"  says  Professor 
Tyndall ;  and  then,  he  ventures  to  believe,  it  will  answer 
all  demands,  carrying  "  the  promise  and  potency  of  all 
terrestrial  life."  If  the  measure  of  the  required  "  change 
in  our  notions  "  had  been  specified,  the  proposition  would 

1  Bishop  Butler's  reply  to  the  Lucretian  in  the  '  Belfast  Address '  is  alJ 
in  the  same  strain. 


842  INTRODUCTION. 

have  had  a  real  meaning,  and  been  susceptible  of  a  test. 
It  is  easy  travelling  through  the  stages  of  such  an  hypo- 
thesis ;  you  deposit  at  your  bank  a  round  sum  ere  you 
start,  and,  drawing  on  it  piecemeal  at  every  pause,  com- 
plete your  grand  tour  without  a  debt.' 

The  last  paragraph  of  this  argument  is  forcibly 
and  ably  stated.  On  it  I  am  willing  to  try  conclusions 
with  Mr.  Martineau.  I  may  say,  in  passing,  that  I  share 
his  contempt  for  the  picturesque  interpretation  of  nature, 
if  accuracy  of  vision  be  thereby  impaired.  But  the  term 
Vorstellungs-fahigkeit,  as  used  by  ine,  means  the  power  of 
definite  mental  presentation,  of  attaching  to  words  the 
corresponding  objects  of  thought,  and  of  seeing  these  in 
their  proper  relations,  without  the  interior  haze  and  soft 
penumbral  borders  which  the  theologian  loves.  To  this 
mode  of  'interpreting  nature'  I  shall  to  the  best  of  my 
ability  now  adhere. 

Neither  of  us,  I  trust,  will  be  afraid  or  ashamed  to 
begin  at  the  alphabet  of  this  question.  Our  first  effort 
must  be  to  understand  each  other,  and  this  mutual  under- 
standing can  only  be  ensured  by  beginning  low  down. 
Physically  speaking,  however,  we  need  not  go  below  the 
sea-level.  Let  us  then  travel  in  company  to  the  Caribbean 
Sea,  and  halt  upon  the  heated  water.  What  is  that  sea, 
and  what  is  the  sun  which  heats  it  ?  Answering  for  my* 
self,  I  say  that  they  are  both  matter.  I  fill  a  glass  with 
the  sea-water  and  expose  it  on  the  deck  of  the  vessel ;  after 
some  time  the  liquid  has  all  disappeared,  and  left  a  solid 
residue  of  salts  in  the  glass  behind.  We  have  mobility, 
invisibility — apparent  annihilation.  In  virtue  of 

The  glad  and  secret  aid 
The  sun  unto  the  ocean  paid, 

the  water  has  taken  to  itself  wings  and  flown  off  as 
vapour.  From  the  whole  surface  of  the  Caribbean  Sea 
such  vapour  is  rising :  and  now  we  must  follow  it — not 


INTRODUCTION.  343 

upon  our  legs,  however,  nor  in  a  ship,  nor  even  in  a 
balloon,  but  by  the  mind's  eye — in  other  words,  by  that 
power  of  Vorstellung  which  Mr.  Martineau  knows  so  well, 
and  which  he  so  justly  scorns  when  it  indulges  in  loose 
practices. 

Compounding,  then,  the  northward  motion  of  the 
vapour  with  the  earth's  axial  rotation,  we  track  our  fugitive 
through  the  higher  atmospheric  regions,  obliquely  across 
the  Atlantic  Ocean  to  Western  Europe,  and  on  to  our 
familiar  Alps.  Here  another  wonderful  metamorphosis 
occurs.  Floating  on  the  cold  calm  air,  and  in  presence 
of  the  cold  firmament,  the  vapour  condenses,  not  only 
to  particles  of  water,  but  to  particles  of  crystalline 
water.  These  coalesce  to  stars  of  snow,  which  fall 
upon  the  mountains  in  forms  so  exquisite  that,  when  first 
seen,  they  never  fail  to  excite  rapture.  As  to  beauty,  in- 
deed, they  put  the  work  of  the  lapidary  to  shame,  while 
as  to  accuracy  they  render  concrete  the  abstractions  of 
the  geometer.  Are  these  crystals  '  matter  '  ?  Without 
presuming  to  dogmatise,  I  answer  for  myself  in  the 
affirmative. 

Still,  a  formative  power  has  obviously  here  come  into 
play  which  did  not  manifest  itself  in  either  the  liquid  or 
the  vapour.  The  question  now  is,  Was  not  the  power 
*  potential '  in  both  of  them,  requiring  only  the  proper 
conditions  of  temperature  to  bring  it  into  action  ?  Again 
I  answer  for  myself  in  the  affirmative.  I  am,  however, 
quite  willing  to  discuss  with  Mr.  Martineau  the  alterna- 
tive hypothesis,  that  an  imponderable  formative  soul  unites 
itself  with  the  substance  alter  its  escape  from  the  liquid 
state.  If  he  should  espouse  this  hypothesis,  then  I  should 
demand  of  him  an  immediate  exercise  of  that  Vorstel- 
lungs-f  ahigkeit,  with  which,  in  my  efforts  to  think  clearly, 
I  can  never  dispense.  I  should  ask,  At  what  moment  did 
the  soul  come  in  ?  Did  it  enter  at  once  or  by  degrees 


844  INTRODUCTION. 

perfect  from  the  first,  or  growing  and  perfecting  itself 
contemporaneously  with  its  own  handiwork?  I  should 
also  ask  whether  it  is  localised  or  diffused  ?  Does  it 
move  about  as  a  lonely  builder,  putting  the  bits  of  solid 
water  in  their  places  as  soon  as  the  proper  temperature 
has  set  in  ?  or  is  it  distributed  through  the  entire  mass 
of  the  crystal  ?  If  the  latter,  then  the  soul  has  the  shape 
of  the  crystal ;  but  if  the  former,  then  I  should  enquire 
after  its  shape.  Has  it  legs  or  arms  ?  If  not,  I  would 
ask  it  to  be  made  clear  to  me  how  a  thing  without  these 
appliances  can  act  so  perfectly  the  part  of  a  builder  ?  (I 
insist  on  definition,  and  ask  unusual  questions,  if  haply  I 
might  thereby  banish  unmeaning  words.)  What  were 
the  condition  and  residence  of  the  soul  before  it  joined 
the  crystal  ?  "What  becomes  of  it  when  the  crystal 
is  dissolved  ?  Why  should  a  particular  temperature  be 
needed  before  it  can  exercise  its  vocation  ?  Finally,  is 
the  problem  before  us  in  any  way  simplified  by  the  assump- 
tion of  its  existence  ?  I  think  it  probable  that,  after  a 
full  discussion  of  the  question,  Mr.  Martineau  would  agree 
with  me  in  ascribing  the  building  power  displayed  in  the 
crystal  to  the  bits  of  water  themselves.  At  all  events,  I 
should  count  upon  his  sympathy  so  far  as  to  believe  that 
he  would  consider  any  one  unmannerly  who  would  de- 
nounce me  for  rejecting  this  notion  of  a  separate  soul,  and 
for  holding  the  snow-crystal  to  be  '  matter.' 

But  then  what  an  astonishing  addition  is  here 
made  to  the  powers  of  matter !  Who  would  have  dreamt, 
without  actually  seeing  its  work,  that  such  a  power  was 
locked  up  in  a  drop  of  water?  All  that  we  needed 
to  make  the  action  of  the  liquid  intelligible  was  the 
assumption  of  Mr.  Martineau's  'homogeneous  extended 
atomic  solids,'  smoothly  gliding  over  one  another.  But 
had  we  supposed  the  water  to  be  nothing  more  than  this, 
we  should  have  ignorantly  defrauded  it  of  an  intrinsic 


INTRODUCTION.  345 

architectural  power,  which  the  art  of  man,  even  when 
pushed  to  its  utmost  degree  of  refinement,  is  incompetent 
to  imitate.  I  would  invite  Mr.  Martineau  to  consider  how 
inappropriate  his  figure  of  a  fictitious  bank  deposit  be- 
comes under  these  circumstances.  The  'account  current' 
of  matter  receives  nothing  at  my  hands  which  could  be 
honestly  kept  back  from  it.  If,  then,  <  Democritus  and 
the  mathematicians '  so  defined  matter  as  to  exclude  the 
powers  here  proved  to  belong  to  it,  they  were  clearly 
wrong,  and  Mr.  Martineau,  instead  of  twitting  me  with 
my  departure  from  them,  ought  rather  to  applaud  me  for 
correcting  them. 

The  reader  of  my  small  contributions  to  the  literature 
which  deals  with  the  overlapping  margins  of  Science  and 
Theology,  will  have  noticed  how  frequently  I  quote  Mr. 
Emerson.  I  do  so  mainly  because  in  him  we  have  a  poet 
and  a  profoundly  religious  man,  who  is  really  and  entirely 
undaunted  by  the  discoveries  of  Science,  past,  present,  or 
prospective.  In  his  case  Poetry,  with  the  joy  of  a  bac- 
chanal, takes  her  graver  brother  Science  by  the  hand,  and 
cheers  him  with  immortal  laughter.  By  Emerson  scientific 
conceptions  are  continually  transmuted  into  the  finer 
forms  and  warmer  hues  of  an  ideal  world.  Our  present 
theme  is  touched  upon  in  the  lines — 

The  journeying  atoms,  primordial  wholes 
Firmly  draw,  firmly  drive  by  their  animate  poles. 

As  regards  veracity  and  insight  these  few  words  outweigh, 
in  my  estimation,  all  the  formal  learning  expended  by 
Mr.  Martineau  in  these  disquisitions  on  Force,  in  which 
he  treats  the  physicist  as  a  conjuror,  and  speaks  so  wittily 
of  atomic  polarity.  In  fact,  without  this  notion  of  polarity 
— this  '  drawing  '  and  '  driving ' — this  attraction  and  re- 
pulsion, we  stand  as  stupidly  dumb  before  the  phenomena 
of  Crystallisation  as  a  Bushman  before  the  phenomena  of 
the  Solar  System.  The  genesis  and  growth  of  the  notion 


846  INTRODUCTION. 

I  have  endeavoured  to  make  clear  in  my  third  Lecture  on 
Light,  and  in  the  article  '  Crystals  and  Molecular  Force  ' 
published  in  this  volume. 

Our  further  course  is  here  foreshadowed.  A  Sunday 
or  two  ago  I  stood  under  an  oak  planted  by  Sir  John 
Moore,  the  hero  of  Corunna.  On  the  ground  near  the  tree 
little  oaklets  were  successfully  fighting  for  life  with  the 
surrounding  vegetation.  The  acorns  had  dropped  into  the 
friendly  soil,  and  this  was  the  result  of  their  interaction. 
What  is  the  acorn  ?  what  the  earth  ?  and  what  the  sun, 
without  whose  heat  and  light  the  tree  could  not  become  a 
tree,  however  rich  the  soil,  and  however  healthy  the  seed? 
I  answer  for  myself  as  before — all  '  matter.'  And  the  heat 
and  light  which  here  play  so  potent  a  part  are  acknow- 
ledged to  be  motions  of  matter.  By  taking  something 
much  lower  down  in  the  vegetable  kingdom  than  the  oak, 
we  might  approach  much  more  nearly  to  the  case  of  crys- 
tallisation already  discussed ;  but  this  is  not  now  necessary. 

If,  instead  of  conceding  the  sufficiency  of  matter  here, 
Mr.  Martineau  should  fly  to  the  hypothesis  of  a  vegetative 
soul,  all  the  questions  before  asked  in  relation  to  the  snow- 
star  become  pertinent.  I  would  invite  him  to  go  over 
them  one  by  one.  and  consider  what  replies  he  will  make  to 
them.  He  may  retort  by  asking  me,  '  Who  infused  the 
principle  of  life  into  the  tree  ?  '  I  say,  in  answer,  that  our 
present  question  is  not  this,  but  another — not  who  made 
the  tree,  but  what  is  it  ?  Is  there  anything  besides 
matter  in  the  tree?  If  so,  what,  and  where?  Mr.  Mar- 
tineau may  have  begun  by  this  time  to  discern  that  it  is 
not  *  picturesqueness,'  but  cold  precision,  that  my  Vor- 
stellungs-fahigkeit  demands.  How,  I  would  ask,  is  this 
vegetative  soul  to  be  presented  to  the  mind  ?  where  did  it 
flourish  before  the  tree  grew  ?  and  what  will  become  of  it 
when  the  tree  is  sawn  into  planks,  or  consumed  in  fire  ? 

Possibly  Mr.  Martineau  may  consider  the  assumption 


INTRODUCTION.  347 

of  this  soul  to  be  as  untenable  and  as  useless  as  I  do.  But 
then  if  the  power  to  build  a  tree  be  conceded  to  pure 
matter,  what  an  amazing  expansion  of  our  notions  of  the 
*  potency  of  matter '  is  implied  in  the  concession !  Think  of 
the  acorn,  of  the  earth,  and  of  the  solar  light  and  heat — 
was  ever  such  necromancy  dreamt  of  as  the  production  of 
that  massive  trunk,  those  swaying  boughs  and  whispering 
leaves,  from  the  interaction  of  these  three  factors  ?  In  this 
interaction,  moreover,  consists  what  we  call  life.  It  will 
be  seen  that  I  am  not  in  the  least  insensible  to  the 
wonder  of  the  tree ;  nay,  I  should  not  be  surprised  if,  in 
the  presence  of  this  wonder,  I  feel  more  perplexed  and 
overwhelmed  than  Mr.  Martineau  himself. 

Consider  it  for  a  moment.  There  is  an  experiment, 
first  made  by  Wheatstone,  where  the  music  of  a  piano  is 
transferred  from  its  sound-board,  through  a  thin  wooden 
rod,  across  several  silent  rooms  in  succession,  and  poured 
out  at  a  distance  from  the  instrument.  The  strings  of 
the  piano  vibrate,  not  singly,  but  ten  at  a  time.  Every 
string  subdivides,  yielding  not  one  note,  but  a  dozen.  All 
these  vibrations  and  subvibrations  are  crowded  together 
into  a  bit  of  deal  not  more  than  a  quarter  of  a  square  inch 
in  section.  Yet  no  note  is  lost.  Each  vibration  asserts 
its  individual  rights  ;  and  all  are,  at  last,  shaken  forth 
into  the  air  by  a  second  sound-board,  against  which  the 
distant  end  of  the  rod  presses.  Thought  ends  in  amaze- 
ment when  it  seeks  to  realise  the  motions  of  that  rod  as 
the  music  flows  through  it.  I  turn  to  my  tree  and 
obs<  eve  its  roots,  its  trunk,  its  branches,  and  its  leaves. 
As  the  rod  conveys  the  music,  and  yields  it  up  to  the 
distant  air,  so  does  the  trunk  convey  the  matter  and  the 
motion — the  shocks  and  pulses  and  other  vital  actions — 
which  eventually  emerge  in  the  umbrageous  foliage 
of  the  tree.  I  went  some  time  ago  through  the  green- 
bouse  of  a  friend.  He  had  ferns  from  Ceylon,  the 


348  INTRODUCTION. 

branches  of  which  were  in  some  cases  not  much  thicker 
than  an  ordinary  pin — hard,  smooth,  and  c}7lindrical — 
often  leafless  for  a  foot  and  more.  But  at  the  end  of  every 
one  of  them  the  unsightly  twig  unlocked  the  exuberant 
oeauty  hidden  within  it,  and  broke  forth  into  a  mass  of 
fronds,  almost  large  enough  to  fill  the  arms.  We  stand  here 
upon  a  higher  level  of  the  wonderful :  we  are  conscious  of 
a  music  subtler  than  that  of  the  piano,  passing  unheard 
through  these  tiny  boughs,  and  issuing  in  what  Mr. 
Martineau  would  opulently  call  the  '  clustered  magnifi- 
cence' of  the  leaves.  Does  it  lessen  my  amazement 
to  know  that  every  cluster,  and  every  leaf — their  form 
and  texture — lie,  like  the  music  in  the  rod,  in  the 
molecular  structure  of  these  apparently  insignificant 
stems?  Not  so.  Mr.  Martineau  weeps  for  'the  beauty  ol 
the  flower  fading  into  a  necessity.'  I  care  not  whether 
it  comes  to  me  through  necessity  or  through  freedom, 
my  delight  in  it  is  all  the  same.  I  see  what  he  sees  with 
a  wonder  superadded.  To  me  as  to  him — nay,  to  me 
more  than  to  him — not  even  Solomon  in  all  his  glory  was 
arrayed  like  one  of  these. 

I  have  spoken  above  as  if  the  assumption  of  a  soul 
would  save  Mr.  Martineau  from  the  inconsistency  of 
crediting  pure  matter  with  the  astonishing  building  power 
displayed  in  crystals  and  trees.  This,  however,  would  not 
be  the  necessary  result ;  for  it  would  remain  to  be  proved 
that  the  soul  assumed  is  not  itself  matter.  When  a  boy 
I  learnt  from  Dr.  Watts  that  the  souls  of  conscious  brutes 
are  mere  matter.  And  the  man  who  would  claim  for 
matter  the  human  soul  itself,  would  find  himself  in  very 
orthodox  company.  *  All  that  is  created,'  says  Faust e,  a 
famous  French  bishop  of  the  fifth  century,  'is  matter. 
The  soul  occupies  a  place  ;  it  is  enclosed  in  a  body ;  it  quits 
the  body  at  death,  and  returns  to  it  at  the  resurrection, 
as  in  the  case  of  Lazarus  ;  the  distinction  between  Hell 


INTRODUCTION.  349 

and  Heaven,  between  eternal  pleasures  and  eternal  pains, 
proves  that,  even  after  death,  souls  occupy  a  place  and  are 
corporeal.  God  only  is  incorporeal.'  Tertullian,  moreover, 
was  quite  a  physicist  in  the  definiteness  of  his  conceptions 
regarding  the  soul.  'The  materiality  of  the  soul,'  he  says, 
'  is  evident  from  the  evangelists.  A  human  soul  is  there 
expressly  pictured  as  suffering  in  hell ;  it  is  placed  in  the 
middle  of  a  flame,  its  tongue  feels  a  cruel  agony,  and  it 
implores  a  drop  of  water  at  the  hands  of  a  happier  soul. 
Wanting  materiality,'  adds  Tertullian,  '  all  this  would  be 
without  meaning.'  One  wonders  what  would  have  happened 
to  this  great  Christian  Father  amid  the  roaring  lions  of 
Belfast.  Could  its  excellent  press  have  shielded  him 
from  its  angry  pulpits  as  it  sheltered  me?  ! 

I  have  glanced  at  inorganic  nature — at  the  sea,  and 
the  sun,  and  the  vapour,  and  the  snowflake,  and  at 
organic  nature  as  represented  by  the  fern  and  the  oak. 
That  same  sun  which  warmed  the  water  and  liberated  the 
vapour,  exerts  a  subtler  power  on  the  nutriment  of  the 
tree.  It  takes  hold  of  matter  wholly  unfit  for  the  purposes 
of  nutrition,  separates  its  nutritive  from  its  non-nutritive 
portions,  gives  the  former  to  the  vegetable,  and  carries 
the  others  away.  Planted  in  the  earth,  bathed  by  the  air, 
and  tended  by  the  sun,  the  tree  is  traversed  by  its  sap,  the 
cells  are  formed,  the  woody  fibre  is  spun,  and  the  whole 
is  woven  to  a  texture  wonderful  even  to  the  naked  eye,  but 
a  million-fold  more  so  to  microscopic  vision.  Does  con- 

1  The  foregoing  extracts,  which  M.  Alglave  recently  brought  to  light  for 
the  benefit  of  the  Bishop  of  Orleans,  are  taken  from  the  sixth  Lecture  of  the 
'  Cours  d'Histoire  Moderne '  of  that  most  orthodox  of  statesmen,  M.  Guizot. 
'  I  could  multiply,'  continues  M.  Guizot, '  these  citations  to  infinity,  and  they 
prove  that  in  the  first  centuries  of  our  era  the  materiality  of  the  soul  was 
an  opinion  not  only  permitted,  but  dcaninant.'  Dr.  Moriarty,  and  the 
synod  which  he  recently  addressed,  obviously  forget  their  own  antecedents. 
Their  boasted  succession  from  the  early  Church  renders  them  the  direct 
offspring  of  a  '  materialism '  more  '  brutal '  than  any  erer  enunciated 
by  me. 


360  INTRODUCTION. 

sciousness  mix  in  any  way  with  these  processes  ?  No  man 
can  tell.  Our  only  ground  for  a  negative  conclusion  is  the 
absence  of  those  outward  manifestations  from  which 
feeling  is  usually  inferred.  But  even  these  are  not 
entirely  absent.  In  the  greenhouses  of  Kew  we  may  see 
that  a  leaf  can  close,  in  response  to  a  proper  stimulus,  as 
promptly  as  the  human  fingers  themselves  ;  and  while 
there  Dr.  Hooker  will  tell  us  of  the  wondrous  fly-catching 
and  fly-devouring  power  of  the  Dionaea.  No  man  can 
say  that  the  feelings  of  the  animal  are  not  represented  by 
a  drowsier  consciousness  in  the  vegetable  world.  At  all 
events,  no  line  has  ever  been  drawn  between  the  conscious 
and  the  unconscious;  for  the  vegetable  shades  into  the 
animal  by  such  fine  gradations,  that  it  is  impossible  to  say 
where  the  one  ends  and  the  other  begins. 

In  all  such  enquiries  we  are  necessarily  limited  by  our 
own  powers :  we  observe  what  our  senses,  armed  with  the 
aids  furnished  by  Science,  enable  us  to  observe ;  nothing 
more.  The  evidences  as  to  consciousness  in  the  vegetable 
world  depend  wholly  upon  our  capacity  to  observe  and  weigh 
them.  Alter  the  capacity,  and  the  evidence  would  alter 
too.  Would  that  which  to  us  is  a  total  absence  of  any 
manifestation  of  consciousness  be  the  same  to  a  being  with 
our  capacities  indefinitely  multiplied?  To  such  a  being 
I  can  imagine  not  only  the  vegetable,  but  the  mineral 
world,  responsive  to  the  proper  irritants,  the  response 
differing  only  in  degree  from  those  exaggerated  manifesta- 
tions, which,  in  virtue  of  their  grossness,  appeal  to  our 
weak  powers  of  observation. 

Our  conclusions,  however,  must  be  based,  not  on 
powers  that  we  can  imagine,  but  upon  those  that  we  possess. 
What  do  they  reveal  ?  As  the  earth  and  atmosphere  offer 
themselves  as  the  nutriment  of  the  vegetable  world,  so 
does  the  latter,  which  contains  no  constituent  not  found 
in  inorganic  nature,  offer  itself  to  the  animal  world. 


INTRODUCTION.  351 

Mixed  with  certain  inorganic  substances — water,  for 
example — the  vegetable  constitutes,  in  the  long  run,  the 
sole  sustenance  of  the  animal.  Animals  may  be  divided 
into  two  classes,  the  first  of  which  can  utilise  the  vegetable 
world  immediately,  having  chemical  forces  strong  enough 
to  cope  with  its  most  refractory  parts  ;  the  second  class 
use  the  vegetable  world  mediately  ;  that  is  to  say,  after  its 
finer  portions  have  been  extracted  and  stored  up  by  the 
first.  But  in  neither  class  have  we  an  atom  newly  created. 
The  animal  world  is,  so  to  say,  a  distillation  through  the 
vegetable  world  from  inorganic  nature. 

From  this  point  of  view  all  three  worlds  would  consti- 
tute a  unity,  in  which  I  picture  life  as  immanent  every- 
where. Nor  am  I  anxious  to  shut  out  the  idea  that  the  life 
here  spoken  of,  may  be  but  a  subordinate  part  and  function 
of  a  Higher  Life,  as  the  living,  moving  blood  is  subordi- 
nate to  the  living  man.  I  resist  no  such  idea  as  long  as 
it  is  not  dogmatically  imposed.  Left  for  the  human  mind 
freely  to  operate  upon,  the  idea  has  ethical  vitality  ;  but, 
stiffened  into  a  dogma,  the  inner  force  disappears,  and  the 
outward  yoke  of  a  usurping  hierarchy  takes  its  place. 

The  problem  before  us  is,  at  all  events,  capable  of 
definite  statement.  We  have  on  the  one  hand  strong 
grounds  for  concluding  that  the  earth  was  once  a  molten 
mass.  We  now  find  it  not  only  swathed  by  an  atmo- 
sphere, and  covered  by  a  sea,  but  also  crowded  with  living 
things.  The  question  is,  How  were  they  introduced  ? 
Certainty  may  be  as  unattainable  here  as  Bishop  Butler 
held  it  to  be  in  matters  of  religion ;  but  in  the  contempla- 
tion of  probabilities  the  thoughtful  mind  is  forced  to  take  a 
side.  The  conclusion  of  Science,  which  recognises  unbroken 
causal  connection  between  the  past  and  the  present,  would 
undoubtedly  be  that  the  molten  earth  contained  within 
it  elements  of  life,  which  grouped  themselves  into  their 
present  forms  as  the  planet  cooled.  The  difficulty  and  re- 


352  INTRODUCTION. 

luctance  encountered  by  this  conception,  arise  solely  from 
the  fact  that  the  theologic  conception  obtained  a  prior 
footing  in  the  human  mind.  Did  the  latter  depend  upon 
reasoning  alone,  it  could  not  hold  its  ground  for  an  hour 
against  its  rival.  But  it  is  warmed  into  life  and  strength 
by  associated  hopes,  fears,  and  expectations — and  not 
only  by  these,  which  are  more  or  less  mean,  but  by  that 
loftiness  of  thought  and  feeling  which  lifts  its  possessoi 
above  the  atmosphere  of  self,  and  which  the  theologic 
idea,  in  its  nobler  forms,  has  through  ages  engendered 
in  noble  minds. 

Were  not  man's  origin  implicated,  we  should  accept 
without  a  murmur  the  derivation  of  animal  and  vegetable 
life  from  what  we  call  inorganic  nature.  The  conclu- 
sion of  pure  intellect  points  this  way  and  no  other.  But 
this  purity  is  troubled  by  our  interests  in  this  life,  and  by 
our  hopes  and  fears  regarding  the  life  to  come.  Reason 
is  traversed  by  the  emotions,  anger  rising  in  the  weaker 
heads  to  the  height  of  suggesting  that  the  compendious 
shooting  of  the  enquirer  would  be  an  act  agreeable  to  God 
and  serviceable  to  man.  But  this  foolishness  is  more  than 
neutralised  by  the  sympathy  of  the  wise  ;  and  in  England 
at  least,  so  long  as  the  courtesy  which  befits  an  earnest 
theme  is  adhered  to,  such  sympathy  is  ever  ready  for  an 
honest  man.  None  of  us  here  need  shrink  from  saying 
all  that  he  has  a  right  to  say.  We  ought,  however,  to  re- 
member that  it  is  not  only  a  band  of  Jesuits,  weaving  their 
schemes  of  intellectual  slavery,  under  the  innocent  guise  of 
'  education,'  that  we  are  opposing.  Our  foes  are  to  some 
extent  they  of  our  own  household,  including  not  only  the 
ignorant  and  the  passionate,  but  a  minority  of  minds  of 
high  calibre  and  culture,  lovers  of  freedom,  moreover,  who, 
though  its  objective  hull  be  riddled  by  logic,  still  find  the 
ethic  life  of  their  religion  unimpaired.  But  while  such  con- 
siderations ought  to  influence  the  form  of  our  argument, 


INTKODUCTION.  353 

and  prevent  it  from  ever  slipping  out  of  the  region  of 
courtesy  into  that  of  scorn  or  abuse,  its  substance,  I  think, 
ought  to  be  maintained  and  presented  in  unmitigated 
strength. 

In  the  year  1855  the  chair  of  philosophy  in  the  Uni- 
versity of  Munich  happened  to  be  filled  by  a  Catholic  priest 
of  great  critical  penetration,  great  learning,  and  great 
courage,  who  bore  the  brunt  of  battle  long  before  D61- 
linger.  His  Jesuit  colleagues,  he  knew,  inculcated  the 
belief  that  every  human  soul  is  sent  into  the  world  from 
(rod  by  a  separate  and  supernatural  act  of  creation.  In  a 
work  entitled  « The  Origin  of  the  Human  Soul,'  Professor 
Frohschammer,  the  philosopher  here  alluded  to,  was  hardy 
enough  to  question  this  doctrine,  and  to  affirm  that  man, 
body  and  soul,  comes  from  his  parents,  the  act  of  creation 
being,  therefore,  mediate  and  secondary  only.  The  Jesuits 
keep  a  sharp  look  out  on  all  temerities  of  this  kind,  and 
their  organ,  the  '  Civilta  Cattolica,'  immediately  pounced 
upon  Frohschammer.  His  book  was  branded  as  'pestilent,' 
placed  in  the  Index,  and  stamped  with  the  condemna- 
tion of  the  Church.1 

It  will  be  seen  in  the  '  Apology  for  the  Belfast  Address ' 
how  simply  and  beautifully  the  great  Jesuit  Perrone  causes 
the  Almighty  to  play  with  the  sun  and  planets,  desiring 
this  one  to  stop,  and  another  to  move,  according  to  His 
pleasure.  To  Perrone's  Vorstellung  God  is  obviously  a 
large  Individual  who  holds  the  leading-strings  of  the 
Universe,  and  orders  its  steps  from  a  position  outside  it 
all.  Nor  does  the  notion  now  under  consideration  err  on  the 

1  King  Maximilian  II.  brought  Liebig  to  Munich,  he  helped  Helmholtz  in 
his  researches,  and  loved  to  liberate  and  foster  science.  But  through  his 
liberal  concession  of  power  to  the  Jesuits  in  the  schools,  he  did  far  more 
damage  10  the  intellectual  freedom  of  his  country  than  his  superstitious  pre- 
decessor Ludwig  I.  Priding  himself  on  being  a  German  prince,  Lurlwig 
•would  not  tolerate  the  interference  of  the  Roman  party  with  the  political 
affairs  of  Bavaria. 


354  INTRODUCTION. 

score  of  indefiniteness.  According  to  it,  the  Power  whom 
Goethe  does  not  dare  to  name,  and  whom  Grassendi  and 
Clerk  Maxwell  present  to  us  under  the  guise  of  a  '  Manu- 
facturer' of  atoms,  turns  out  annually,  for  England  and 
Wales  alone,  a  quarter  of  a  million  of  new  souls.  Taken 
in  connection  with  the  dictum  of  Mr.  Carlyle,  that  this 
annual  increment  to  our  population  are  'mostly  fools,'  but 
little  profit  to  the  human  heart  seems  derivable  from  this 
mode  of  regarding  the  Divine  operations. 

But  if  the  Jesuit  notion  be  rejected,  what  are  we  to 
accept  ?  Physiologists  say  that  every  human  being  comes 
from  an  egg,  not  more  than  the  y^^th  of  an  inch  in  diameter. 
Is  this  egg  matter  ?  I  hold  it  to  be  so,  as  much  as  the  seed 
of  a  fern  or  of  an  oak.  Nine  months  go  to  the  making  of  it 
into  a  man.  Are  the  additions  made  during  this  period  of 
gestation  drawn  from  matter  ?  I  think  so  undoubtedly.  If 
there  be  anything  besides  matter  in  the  egg,  or  in  the  in- 
fant subsequently  slumbering  in  the  womb,  what  is  it  ?  The 
questions  already  asked  with  reference  to  the  stars  of  snow 
may  be  here  repeated.  Mr.  Martineau  will  complain  that 
I  am  disenchanting  the  babe  of  its  wonder ;  but.  is  this  the 
case  ?  I  figure  it  growing  in  the  womb,  woven  by  a  some- 
thing not  itself,  without  conscious  participation  on  the 
part  of  either  father  or  mother,  and  appearing  in  due 
time,  a  living  miracle,  with  all  its  organs  and  all  their 
implications.  Consider  the  work  accomplished  during 
these  nine  months  in  forming  the  eye  alone — with  its  lens, 
and  its  humours,  and  its  miraculous  retina  behind.  Con- 
sider the  ear  with  its  tympanum,  cochlea,  and  Corti's 
organ — an  instrument  of  three  thousand  strings,  built 
adjacent  to  the  brain,  and  employed  by  it  to  sift, 
separate,  and  interpret,  antecedent  to  all  consciousness, 
the  sonorous  tremors  of  the  external  world.  All  this  has 
been  accomplished,  not  only  without  man's  contriv- 
ance, but  without  his  knowledge,  the  secret  of  his  own 


INTRODUCTION.  355 

organisation  having  been  withheld  from  him  since  his 
birth  in  the  immeasurable  past,  until  the  other  day. 
Matter  I  define  as  that  mysterious  tiling  by  which  all 
this  is  accomplished.  How  it  came  to  have  this  power 
is  a  question  on  which  I  never  ventured  an  opinion.  If, 
then,  Matter  starts  as  l  a  beggar,'  it  is,  in  my  view, 
because  the  Jacobs  of  theology  have  deprived  it  of  its 
birthright.  Mr.  Martineau  need  fear  no  disenchantment. 
Theories  of  evolution  go  but  a  short  way  towards  the 
explanation  of  this  mystery ;  while,  in  its  presence,  the 
notion  of  an  atomic  Manufacturer  and  Artificer  of  souls 
raises  the  doubt,  whether  those  who  entertain  it  were  ever 
really  penetrated  by  the  solemnity  of  the  problem  for 
which  they  offer  such  a  solution. 

There  are  men,  and  they  include  amongst  them  some 
of  the  best  of  the  race  of  men,  upon  whose  minds  this 
mystery  falls  without  producing  either  warmth  or  colour. 
The  '  dry  light '  of  the  intellect  suffices  for  them,  and 
they  live  their  noble  lives  untouched  by  a  desire  to  give 
the  mystery  shape  or  expression.  There  are,  on  the  other 
hand,  men  whose  minds  are  warmed  and  coloured  by  its 
presence,  and  who,  under  its  stimulus,  attain  to  moral 
heights  which  have  never  been  overtopped.  Different 
spiritual  climates  are  necessary  for  the  healthy  existence 
of  these  two  classes  of  men  ;  and  different  climates  must 
be  accorded  them.  The  history  of  humanity,  however, 
proves  the  experience  of  the  second  class  to  illustrate  the 
most  pervading  need.  The  world  will  have  religion  of 
some  kind,  even  though  it  should  fly  for  it  to  the  intel- 
lectual whoredom  of  '  spiritualism.'  What  is  really  wanted 
is  the  lifting  power  of  an  ideal  element  in  human  life. 
But  the  free  play  of  this  power  must  be  preceded  by  its 
release  from  the  torn  swaddling  bands  of  the  past,  and 
from  the  practical  materialism  of  the  present.  It  is  now 
in  danger  of  being  strangled  by  the  one,  or  stupefied  by 


856  INTRODUCTION. 

the  other.  I  look,  however,  forward  to  a  time  when  the 
strength,  insight,  and  elevation  which  now  visit  us  in 
mere  hints  and  glimpses  during  moments  '  of  clearness 
and  vigour,'  shall  be  the  stable  and  permanent  possession 
of  purer  and  mightier  minds  than  ours — purer  and 
mightier,  partly  because  of  their  deeper  knowledge  of 
matter  and  their  more  faithful  conformity  to  its  laws. 

JOHN  TYNDALL. 

ATHEKJBUM  CITJB  :  November  1875. 


I. 

REFLECTIONS  ON  PRAYER  AND  NATURAL  LAW. 

rpHE  aspects  of  nature  are  more  varied  and  impressive  in 
JL  Alpine  regions  than  elsewhere.  The  mountains  in 
their  setting  of  deep  blue  sky  ;  the  glow  of  firmament  and 
peaks  at  sunrise  and  sunset ;  the  formation  and  distribu- 
tion of  clouds ;  the  descent  of  rain,  hail,  and  snow ;  the 
stealthy  slide  of  glaciers  and  the  rush  of  avalanches  and 
rivers ;  the  fury  of  storms ;  thunder  and  lightning,  with 
their  occasional  accompaniment  of  blazing  woods ; — all 
these  things  tend  to  excite  the  feelings  and  to  bewilder 
the  mind.  In  this  entanglement  of  phenomena  it  seems 
hopeless  to  seek  for  law  or  orderly  connection.  And  before 
the  thought  of  law  dawned  upon  the  human  mind,  men 
naturally  referred  these  inexplicable  effects  to  personal 
agency.  In  the  fall  of  a  cataract  the  savage  saw  the  leap 
of  a  spirit,  and  the  echoed  thunder-peal  was  to  him  the 
hammer-clang  of  an  exasperated  god.  Propitiation  of 
these  terrible  powers  was  the  consequence,  and  sacrifice 
was  offered  to  the  demons  of  earth  and  air. 

But  observation  tends  to  chasten  the  emotions  and  to 
check  those  structural  efforts  of  the  intellect  which  have 
emotion  for  their  base.  One  by  one  natural  phenomena 
have  been  associated  with  their  proximate  causes  ;  and 
the  idea  of  direct  personal  volition  mixing  itself  with  the 
economy  of  nature  is  retreating  more  and  more.  Many 
of  us  fear  this  tendency.  Our  faith  and  fselings  are  dear 


358  FRAGMENTS   OP   SCIENCE. 

to  us,  and  we  look  with  suspicion  and  dislike  on  any 
philosophy,  the  apparent  tendency  of  which  is  to  dry  up 
the  soul.  Probably  every  change  from  ancient  savagery 
to  our  present  enlightenment  has  excited,  in  a  greater  or 
less  degree,  a  fear  of  this  kind.  But  the  fact  is,  that  we 
have  not  yet  determined  whether  its  present  form  is 
necessary  to  the  life  and  warmth  of  religious  feeling.  We 
may  err  in  linking  the  imperishable  with  the  transitory, 
and  confound  the  living  plant  with  the  decaying  pole  to 
which  it  clings.  My  object,  however,  at  present  is  not 
to  argue,  but  to  mark  a  tendency.  We  have  ceased  to 
propitiate  the  powers  of  nature — ceased  even  to  pray  for 
things  in  manifest  contradiction  to  natural  laws.  In 
Protestant  countries,  at  least,  I  think  it  is  conceded  that 
the  age  of  miracles  is  past. 

At  the  auberge  near  the  foot  of  the  Rhone  glacier, 
I  met,  in  the  summer  of  1858,  an  athletic  young  priest, 
who,  after  a  solid  breakfast,  including  a  bottle  of  wine, 
informed  me  that  he  had  come  up  to  '  bless  the  mountains.' 
This  was  the  annual  custom  of  the  place.  Year  by  year 
the  Highest  was  entreated,  by  official  intercessors,  to  make 
such  meteorological  arrangements  as  should  ensure  food 
and  shelter  for  the  flocks  and  herds  of  the  Valaisians.  A 
diversion  of  the  Rhone,  or  a  deepening  of  the  river's  bed, 
would,  at  the  time  I  now  mention,  have  been  of  incalculable 
benefit  to  the  inhabitants  of  the  valley.  But  the  priest 
would  have  shrunk  from  the  idea  of  asking  the  Omni- 
potent to  open  a  new  channel  for  the  river,  or  to  cause  a 
portion  of  it  to  flow  over  the  Grimsel  pass,  and  down  the 
vale  of  Oberhasli  to  Brientz.  This  he  would  have  deemed 
a  miracle,  and  he  did  not  come  to  ask  the  Creator  to 
perform  miracles,  but  to  do  something  which  he  manifestly 
thought  lay  quite  within  the  bounds  of  the  natural  and 
non-miraculous.  A  Protestant  gentleman  who  was  present 
at  the  time  smiled  at  this  recital.  He  had  no  faith  in 


REFLECTIONS  ON  PRAYER  AND  NATURAL  LAW.   359 

the  priest's  blessing- ;  still,  he  deemed  his  prayer  different 
in  kind  from  a  request  to  open  a  new  river-cut,  or  to  cause 
the  water  to  flow  up-hill. 

In  a  similar  manner  self-satisfied  Protestants  smile 
at  the  honest  Tyrolese  priest,  who,  when  he  feared  the 
bursting  of  a  glacier  dam,  offered  the  sacrifice  of  the  Mass 
upon  the  ice  as  a  means  of  averting  the  calamity.  That 
poor  man  did  not  expect  to  convert  the  ice  into  adamant, 
or  to  strengthen  its  texture,  so  as  to  enable  it  to  withstand 
the  pressure  of  the  water  ;  nor  did  he  expect  that  his 
sacrifice  would  cause  the  stream  to  roll  back  upon  its 
source  and  relieve  him,  by  a  miracle,  of  its  presence.  But 
beyond  the  boundaries  of  his  knowledge  lay  a  region  where 
rain  was  generated,  he  knew  not  how.  He  was  not  so 
presumptuous  as  to  expect  a  miracle,  but  he  firmly  believed 
that  in  yonder  cloud-land  matters  could  be  so  arranged, 
without  trespass  on  the  miraculous,  that  the  stream  which 
threatened  him  and  his  flock  should  be  caused  to  shrink 
within  its  proper  bounds. 

Both  these  priests  fashioned  that  which  they  did  not 
understand  to  their  respective  wants  and  wishes.  In  their 
case  imagination  came  into  play,  unconditioned  by  a  know- 
ledge of  laws.  A  similar  state  of  mind  was  long  prevalent 
among  mechanicians.  Many  of  these,  and  some  of  them 
extremely  skilful  ones,  were  occupied  a  century  ago  with 
the  question  of  perpetual  motion.  They  aimed  at  con- 
structing a  machine  which  should  execute  work  without 
the  expenditure  of  power  ;  and  some  of  them  went  mad 
in  the  pursuit  of  this  object.  The  faith  in  such  a  con- 
summation, involving,  as  it  did,  immense  personal  profit 
to  the  inventor,  was  extremely  exciting,  and  every  attempt 
to  destroy  this  faith  was  met  by  bitter  resentment  on  the 
part  of  those  who  held  it.  Gradually,  however,  as  men 
became  more  and  more  acquainted  with  the  true  functions 
of  machinery,  the  dream  dissolved.  The  hope  of  getting 


800  FRAGMENTS   OP  SCIENCE. 

work  out  of  mere  mechanical  combinations  disappeared  •, 
but  still  there  remained  for  the  speculator  a  cloud-land 
denser  than  that  which  filled  the  imagination  of  the 
Tyrolese  priest,  out  of  which  he  still  hoped  to  evolve  per- 
petual motion.  There  was  the  mystic  store  of  chemic 
force,  which  nobody  understood;  there  were  heat  and 
light,  electricity  and  magnetism,  all  competent  to  produce 
mechanical  motions.1  Here,  then,  is  the  mine  in  which 
we  must  seek  our  gem.  A  modified  and  more  refined 
form  of  the  ancient  faith  revived ;  and,  for  aught  I  know, 
a  remnant  of  sanguine  designers  may  at  the  present 
moment  be  engaged  on  the  problem  which  like-minded 
men  in  former  ages  left  unsolved. 

And  why  should  a  perpetual  motion,  even  under 
modern  conditions,  be  impossible  ?  The  answer  to  this 
question  is  the  statement  of  that  great  generalisation  of 
modern  science,  which  is  known  under  the  name  of  the 
Conservation  of  Energy.  This  principle  asserts  that  no 
power  can  make  its  appearance  in  nature  without  an 
equivalent  expenditure  of  some  other  power  ;  that  natural 
agents  are  so  related  to  each  other  as  to  be  mutually  con- 
vertible, but  that  no  new  agency  is  created.  Light  runs 
into  heat ;  heat  into  electricity;  electricity  into  magnetism; 
magnetism  into  mechanical  force  ;  and  mechanical  force 
again  into  light  and  heat.  The  Proteus  changes,  but  he 
is  ever  the  same  ;  and  his  changes  in  nature,  supposing 
no  miracle  to  supervene,  are  the  expression,  not  of  spon- 
taneity, but  of  physical  necessity.  A  perpetual  motion, 
then,  is  deemed  impossible,  because  it  demands  the  creation 
of  force,  whereas  the  principle  of  Conservation  is — no 
creation,  but  infinite  conversion. 

It  is  an  old  remark  that  the  law  which  moulds  a  tear 
also  rounds  a  planet.  In  the  application  of  law  in  nature 

1  See  Helmholtz  — '  Wechselwirkung  der  Naturkrafte.' 


REFLECTIONS    OX   PKAYER   AND   NATURAL    LAW.      301 

the  terms  great  and  small  are  unknown.  Thus  the  prin- 
ciple referred  to  teaches  us  that  the  Italian  wind,  gliding 
over  the  crest  of  the  Matterhorn,  is  as  firmly  ruled  as  the 
earth  in  its  orbital  revolution  round  the  sun ;  and  that 
the  fall  of  its  vapour  into  clouds  is  exactly  as  much  a 
matter  of  necessity  as  the  return  of  the  seasons.  The 
dispersion,  therefore,  of  the  slightest  mist  by  the  special 
volition  of  the  Eternal,  would  be  as  much  a  miracle  as 
the  rolling  of  the  Khone  over  the  Grimsel  precipices,  down 
the  valley  of  Hasli  to  Meyringen  and  Brientz. 

It  seems  to  me  quite  beyond  the  present  power  of 
science  to  demonstrate  that  the  Tyrolese  priest,  or  his 
colleague  of  the  Ehone  valley,  asked  for  an  '  impossibility ' 
in  praying  for  good  weather ;  but  Science  can  demonstrate 
the  incompleteness  of  the  knowledge  of  nature  which 
limited  their  prayers  to  this  narrow  ground ;  and  she  may 
lessen  the  number  of  instances  in  which  we  '  ask  amiss,' 
by  showing  that  we  sometimes  pray  for  the  performance 
of  a  miracle  when  we  do  not  intend  it.  She  does  assert, 
for  example,  that  without  a  disturbance  of  natural  law, 
quite  as  serious  as  the  stoppage  of  an  eclipse,  or  the 
rolling  of  the  St.  Lawrence  up  the  Falls  of  Niagara,  no 
act  of  humiliation,  individual  or  national,  could  call  one 
shower  from  heaven,  or  deflect  towards  us  a  single  beam 
of  the  sun. 

Those,  therefore,  who  believe  that  the  miraculous  is 
still  active  in  nature,  may,  with  perfect  consistency,  join 
in  our  periodic  prayers  for  fair  weather  and  for  rain  :  while 
those  who  hold  that  the  age  of  miracles  is  past,  will,  if 
they  be  consistent,  refuse  to  join  in  such  petitions.  And 
if  these  latter  wish  to  fall  back  upon  such  a  justification, 
they  may  fairly  urge  that  the  latest  conclusions  of  science 
are  in  perfect  accordance  with  the  doctrine  of  the  Master 
himself,  which  manifestly  was  that  the  distribution  of 
natural  phenomena  is  not  affected  by  moral  or  religious 


362  FRAGMENTS    OF   SCIENCE. 

causes.  '  He  maketh  His  sun  to  rise  on  the  evil  and  on 
the  good,  and  sendeth  rain  on  the  jast  and  on  the  unjust.' 
Granting  '  the  power  of  Free  Will  in  man,'  so  strongly 
claimed  by  Professor  Mansel  in  his  admirable  defence  of 
the  belief  in  miracles,  and  assuming  the  efficacy  of  free 
prayer  to  produce  changes  in  external  nature,  it  necessarily 
follows  that  natural  laws  are  more  or  less  at  the  mercy  of 
man's  volition,  and  no  conclusion  founded  on  the  assumed 
permanence  of  those  laws  would  be  worthy  of  confidence. 

It  is  a  wholesome  sign  for  England  that  she  numbers 
among  her  clergy  men  wise  enough  fo  understand  all  this, 
and  courageous  enough  to  act  up  to  their  knowledge.  Such 
men  do  service  to  public  character,  by  encouraging  a  manly 
and  intelligent  conflict  with  the  real  causes  of  disease 
and  scarcity,  instead  of  a  delusive  reliance  on  supernatural 
aid.  But  they  have  also  a  value  beyond  this  local  and 
temporary  one.  They  prepare  the  public  mind  for  changes, 
which  though  inevitable,  could  hardly,  without  such  pre- 
paration, be  wrought  without  violence.  Iron  is  strong ; 
still,  water  in  crystallising  will  shiver  an  iron  envelope, 
and  the  more  unyielding  the  metal  is,  the  worse  for  its 
safety.  There  are  men  amongst  us  who  would  encompass 
philosophic  speculation  by  a  rigid  envelope,  hoping  thereby 
to  restrain  it,  but  in  reality  giving  it  explosive  force.  If 
we  want  an  illustration  of  this  we  have  only  to  look  at 
modern  Rome.  In  England,  thanks  to  men  of  the  stamp 
to  which  I  have  alluded,  scope  is  gradually  given  to  thought 
for  changes  of  aggregation,  and  the  envelope  slowly  alters 
its  form,  in  accordance  with  the  necessities  of  the  time. 


The  foregoing  remarks  were  first  published  in  a  little 
book  of  mine,  entitled  'Mountaineering  in  1861.'     They 


REFLECTIONS    ON   PRAYER   AND   NATURAL   LAW.      3(33 

were  prompted  by  the  obloquy  incurred  by  certain  minis« 
ters  of  the  Church  of  England,  through  their  refusal  to 
join  in  an  act  of  humiliation  with  reference  to  a  bad 
harvest.1  Three  years  after  their  publication  we  were 
threatened  by  cholera  and  invaded  by  the  cattle  plague. 
On  October  5,  1865,  'an  order  in  Council  commanding  a 
special  form  of  prayer  for  the  removal  of  the  cattle  plague, 
and  the  preservation  of  the  country  from  cholera,'  was 
issued,  and  on  October  9,  the  following  article  on  the 
subject  appeared  in  the  'Pall  Mall  Gazette ': — 

PRATERS  AGAINST  THE  CHOLERA. 

It  would  be  affectation  to  disguise  the  fact  that  very 
many  of  the  more  educated  English  laity  look  with  small 
favour  on  the  proposal  that  we  should  all  pray,  as  a  nation, 
for  the  warding  off  of  the  cholera  and  the  removal  of  the 
cattle  plague.  It  is  not  that  they  are  insensible  to  the  claims 
of  religion,  or  that  they  regard  the  physical  universe  as  a 
self-acting  machine  which  has  gone  on  with  its  unconscious 
life  from  all  eternity,  or  that  they  object  to  praying  alto- 
gether. Perhaps  there  never  was  a  time  when  a  sincere 
recognition  of  the  force  of  religious  obligation  was  as 
general  among  men  of  learning  and  profound  thought  as 
it  is  at  the  present  moment.  Godlessness  is  not  the  cha- 
racteristic of  our  time.  Its  characteristic  is  an  ever-in- 
creasing conviction  of  the  uniformity  of  the  operations  of 
all  physical  law,  not  as  a  self-existent  necessity,  but  as  a 
result  of  the  fiat  of  the  Eternal  Mind.  As  a  consequence 
of  this  supremacy  of  unchanging  law  it  is  held  that  it  is 
a  transparent  absurdity  to  imagine  that  on  the  petition  of 
any  man  or  any  number  of  men  the  operations  of  natural 
law  will  be  suspended.  To  ask  of  the  Almighty  God  that 

1  On  such  notions  see  quotation  from  Whewell,  page  470. 
18 


364  FRAGMENTS   OF   SCIENCE. 

He  would  alter  the  course  of  the  planets,  or  cause  water  to 
flow  upwards,  would  be  more  startling  in  its  presumptuous 
imbecility,  but  it  would  not  be  more  useless  or  philosophi- 
cally more  extravagant,  than  this  act  of  national  supplica- 
tion to  which  we  are  now  invited.  The  truth  or  error  of 
this  view  is  not  a  fit  subject  for  treatment  in  a  newspaper. 
By  a  wise  though  tacit  understanding,  journalists  for  the 
most  part  abstain  from  handling  the  dogmas  of  Christianity 
and  of  religion  in  general.  But  when  the  Government  of 
the  day  comes  forward  with  a  formal  proposal  that  we 
should  go  out  of  our  way  to  unite  in  a  special  religious  act 
under  the  pressure  of  a  heavy  national  calamity,  it  is  im- 
possible altogether  to  ignore  the  convictions  entertained 
by  very  many  of  the  ablest  and  most  honest  thinkers  of 
the  day.  There  is  no  necessity,  indeed,  to  treat  the  ques- 
tion in  any  way  from  the  dogmatic  point  of  view.  If  we 
venture  on  the  subject  at  all,  it  is  in  order  to  call  attention 
to  certain  phenomena  in  our  every-day  life,  which  appear 
to  furnish  a  clue  to  all  the  real  difficulties  of  the  subject. 
The  facts  of  the  case  are  so  obvious,  and  the  reasoning 
that  they  suggest  is  so  simple,  that  they  may  be  presented 
in  the  shortest  space. 

Certain,  then,  as  it  is,  that  the  laws  of  the  material 
universe  are  absolutely  unchangeable,  it  is  equally  certain 
that  they  are  susceptible  of  a  boundless  variety  of  distinct 
combinations.  Whether  all  organic  forms  and  all  animal 
and  vegetable  life  are,  or  are  not,  the  results  of  the  presence 
of  some  one  hidden  universal  material  agent,  in  operation 
the  phenomena  are  the  same.  The  laws  of  gravity,  of 
chemical  affinity,  of  electric  action,  of  heat,  and  every 
other  force  that  is  concerned  in  carrying  forward  organic 
change  and  vegetable  and  animal  life,  produce  in  reality 
infinite  variations  of  results,  according  to  the  conditions 
under  which  their  powers  are  called  into  action.  These 
combinations  at  one  time  give  birth  to  the  cholera,  at 


INFLECTIONS  ON  PRAYER  AND   NATURAL   LAW.      365 

another  to  the  cattle  plague,  at  another  to  rich  harvests,  at 
another  to  famine.  These  combinations,  moreover,  are  not 
the  result  of  the  boundless  varieties  of  the  action  of 
material  forces  alone.  We  ourselves  imitate  these  fresh 
combinations  every  moment  that  we  live.  Human  life,  in 
fact,  is  carried  on  by  means  of  a  perpetual  struggle  of  the 
human  will  with  the  elementary  laws  of  physical  action. 
The  actual  condition  of  the  material  world  is  totally  unlike 
what  it  would  have  been  if  man  had  never  existed  on  this 
globe.  We  live  upon  the  forms  of  vegetable  and  animal 
life  which  are  created  in  harmony  with  physical  law,  as 
constrained  to  yield  to  our  personal  control.  The  chemical 
condition  of  the  atmosphere  is  modified  by  every  movement 
of  our  lungs,  by  every  fire  we  light,  by  every  candle  we 
blow  out,  by  every  forest  we  plant,  by  every  field  we  drain. 
It  is  not  too  much  to  say  that  the  position  of  the  centre  of 
gravity  in  the  great  globe  itself  can  be  made  to  move,  in 
a  real,  though  to  us  inappreciable  degree,  by  the  alterations 
we  work  in  the  form  of  the  earth's  surface^  The  remedies 
we  are  now  devising  for  the  warding  off  of  the  cholera  are 
in  reality  an  intervention  with  the  modes  of  operation  of 
chemical,  atmospherical,  and  pathological  law.  We  cannot 
alter  these  laws  in  themselves,  but  by  the  exercise  of  our 
wills  we  can  compel  them,  like  the  spirits  in  Oriental  tales 
coerced  by  the  seal  of  the  mighty  Solomon,  to  yield  results 
not  deadly,  but  life-giving.  Thus,  then,  in  a  most  true 
and  real  sense,  the  great  Author  of  physical  law  permits 
us,  if  we  so  please  to  call  it,  to  interfere  with  the  universe 
as  He  originally  created  it.  Or  rather  this  incessant  in- 
terference is  the  very  condition  of  our  own  life ;  and 
physical  law  can  only  be  called  unchangeable  with  the 
proviso  that  it  is  to  this  extent  changeable  at  the  dictates 
of  the  will  of  man. 

Granting,  then,  the  belief  (which  we  are  not  called  on 
to  argue)  that  prayer  is  in  its  essence  a  direct  intercourse 


866  FRAGMENTS   OP   SCIENCE. 

between  rational  beings  and  the  Author  of  physical  laws, 
there  appears  no  scientific  difficulty  in  conceiving  that,  in 
reply  to  our  solicitation,  He  might  himself  institute  fresh 
combinations  in  their  operation  of  the  same  nature  as  those 
which  we  ourselves  undoubtedly  produce  every  hour  that 
we  live.  No  reasonable  person  will  deny  the  abstract 
possibility  of  the  same  modifications  of  the  work  of  law, 
caused  by  the  direct  power  of  God,  which  can  be  accom- 
plished by  us.  It  would,  in  truth,  be  ridiculous  to  doubt 
it.  The  supremacy  and  unchangeableness  of  law  would  be 
in  each  case  untouched.  The  theory  of  those  who  most 
rigorously  deny  the  possibility  of  anything  wearing  the 
semblance  of  miraculous  interference  would  not  be  im- 
pugned by  a  hair's  breadth.  There  is  no  need  to  have  re- 
course to  the  argumentum  ad  verecundiam  of  the  super- 
ficially pious,  who  triumphantly  ask  us  whether  the  Creator 
of  the  universe  cannot  alter  the  laws  that  He  himself  has 
made.  The  men  who  asked  Lord  Palmerston  for  a  fast  day, 
and  for  answer  were  told  to  look  to  their  drainage,  may 
learn  that  the  cleansing  of  sewers  and  the  offering  of 
prayers,  though  two  distinct  outward  acts,  are  in  reality 
of  a  nature  essentially  the  same.  What  we  do  '  immedi- 
ately,' to  use  the  technical  term,  with  our  own  hands,  when 
we  disinfect  our  houses  and  attend  to  our  diet,  and  make 
experiments  in  medicine,  it  is  possible  we  may  also  do 
'mediately,' by  entreating  of  God  that  He  will  supplement 
our  ignorant  efforts  by  physical  means,  which  bear  the 
same  relation  as  our  own  to  existing  laws,  being  solely 
different  in  that  His  knowledge  of  His  own  laws  is  complete, 
while  ours  is  little  more  than  a  tentative  guesswork. 

As  we  have  said,  in  offering  these  suggestions  we  are 
not  meddling  with  the  subject  under  its  more  dogmatic 
aspects.  Still  less  are  we  paying  an  instant's  heed  to  the 
follies  of  the  school  that  looks  upon  these  newly  recurring 
visitations  of  old  diseases  as  'judgments,' or  'punishments,' 


REFLECTIONS  ON  PRATER  AND  NATURAL  LAW.   3(57 

or  as  in  any  sense  differing  from  the  ordinary  organic 
routine  of  animal  life  as  it  goes  on  from  day  to  day  and 
from  age  to  age.  It  is  as  irreligious  as  it  is  unphiloso- 
phical  to  take  the  life  of  a  nation  or  of  a  man,  and  map  it 
out  into  little  sections,  and  call  one  thing  a  judgment  and 
another  a  blessing,  and  even  interpret  these  judgments  and 
blessings  a,«  being  specially  merited  by  our  neighbour's 
sins  or  by  our  own  virtues.  Doubtless  they  are  all  parts 
of  one  mighty  whole  which  we  know  to  be  harmonious 
throughout,  but  which  we  also  know  to  be  so  partially 
understood  that  it  is  absurd  to  classify  its  fragments,  and 
ticket  them  in  accordance  with  the  shallow  prejudices  of 
the  hour.  The  foolishness  of  these  half-pious  and  wholly 
superficial  religionists  does  not  consist  in  their  believing 
that  cholera  and  cattle  plagues  are  of  Divine  origin,  and 
have  a  meaning  and  a  bearing  on  human  life  in  its  highest 
aspects.  It  consists  in  their  impudent  pretence  of  pro- 
phetic gifts,  and  in  the  spiritual  quackery  with  which  they 
recommend  remedies  suggested  only  by  an  immeasurable 
gelf-complacency.  Further,  as  to  this  setting  apart  of  a 
special  time  for  national  supplication,  we  say  nothing 
whatever  concerning  its  wisdom  or  prudence;  and  we  state 
this  without  the  slightest  arriere  pensee  or  reserve.  Our 
aim  is  solely  to  look  at  the  question  on  its  scientific  side, 
and  to  suggest  to  those  who  feel  acutely  the  difficulties 
which  perhaps  they  do  not  like  to  avow,  a  certain  solution 
which  appears  satisfactory,  even  to  the  most  tender  con- 
sciences, and  which  undoubtedly  rests  on  the  undeniable 
facts  of  every-day  life. 


On  the  day  after  its  publication  this  article  reached  my 
hands,  accompanied  by  a  note  commending  it  as  a  fair 
reply  to  my  article  of  1861.  The  friend  who  sent  it  to  me 
was  perfectly  orthodox  and  of  high  rank  among  scientific 


868  FRAGMENTS   OF   SCIENCE. 

men.     I  gave  it  due  consideration,  and  wrote  in  reference 
to  it  the  following  brief  letter  to  the  'Pall  Mall  Gazette':— 

To  tk  •  EDITOR  of  the  '  PALL  MALL  GAZETTE.' 

SIK, — An  eminent  and  respected  scientific  friend  has 
drawn  my  attention  to  your  exceedingly  clever  article 
entitled  '  Prayers  against  Cholera.'  The  position  there 
taken  is  a  strong  one  ;  for,  granting  the  entire  freedom 
of  the  human  will,  that  it,  unlike  natural  phenomena,  is 
uncontrolled  by  its  antecedents,  it  follows  that,  within 
certain  limits,  arbitrary  changes  may  be  wrought  in  the 
order  and  sequence  of  those  phenomena.  And  if  the  possi- 
bility of  such  changes,  even  in  the  smallest  particular,  be 
conceded,  the  abstract  possibility,  or  in  other  words  the 
conceiv ability,  of  a  change  upon  a  grand  scale  follows  as 
a  matter  of  course.  Hence  (you  would  argue)  the  petition- 
ing of  the  Almighty  against  cholera  or  cattle  plague  is 
rescued  from  the  charge  of  necessary  absurdity. 

But  you  will,  I  think,  admit  that  the  value  of  this 
argument  is  not  bounded  by  the  limits  of  nineteenth 
century  Christendom ;  that  it  would  apply  equally  well 
to  the  beliefs  of  ancient  heathens  and  modern  savages, 
who  saw  and  see  in  almost  every  change  of  the  aspects  of 
nature  the  hand  of  an  arbitrary  Deity.  It  justifies  equally 
the  mildest  and  the  most  extravagant  belief  in  spontaneous 
interference.  Who,  indeed,  in  such  a  case,  is  to  draw  the 
line  between  mildness  and  extravagance?  Once  upon  a  time 
we  prayed  against  the  ravages  of  small-pox — with  what 
effect  ?  You  may  answer  (and  rightly  answer)  that  you 
do  not  know.  But  you  will,  at  all  events,  admit  that  the 
prayer,  as  a  preventive  or  remedial  agent,  proved  no 
match  for  vaccination.  Would  the  suppliant  voice  of  a 
whole  nation  have  atoned  for  the  bad  engineering,  or 
caused  a  suspension  of  the  laws  of  hydraulic  pressure,  in 
the  case  of  the  Bradfield  reservoir  ?  I  think  not.  The 


EEFLECTIOXS    ON   PEAYEE    AND   NATUEAL    LAW.      309 

great  majority  of  sane  persons  at  the  present  day  believe 
in  the  necessary  character  of  natural  laws,  and  it  is  only 
where  the  antecedents  of  a  calamity  are  vague  or  disguised 
that  they  think  of  resorting  to  prayer  to  avert  it.  Such 
unhappily  is  the  case  with  the  cholera  and  the  cattle 
plague.  With  regard  to  them  we  are  in  a  state  of  dark- 
ness similar  to  that  of  the  ancient  pagan  world  with  re- 
gard to  natural  phenomena  generally,  and  hence  the  dis- 
position to  resort  to  pagan  methods  of  meeting  these 
scourges. 

JOHN  TYNDALL. 

October  11,  1865. 


On  October  17  the  argument  was  resumed  in  a  second 
article  by  the  'Pall  Mall  Gazette':— 

ON  PRAYER  AND  THE  CHOLERA. 

We  are  tempted  by  Professor  Tyndall's  letter,  which 
we  published  on  Thursday,  to  return  to  the  subject  of  the 
article  which  he  criticises.  He  has,  we  think,  partly 
failed  in  understanding  the  drift  of  our  remarks.  He 
attributes  to  us  a  belief  in  the  l  entire  freedom  of  the 
human  will '  as  being  '  uncontrolled  by  its  antecedents,'  a 
belief  which  we  certainly  neither  expressed  nor  intended 
to  discuss.  We  neither  contrasted  the  operations  of  the 
will  with  '  natural  phenomena,'  nor  did  we  attempt  any 
definition  of  its  nature  or  powers.  We  simply  took  the 
'  human  will '  as  a  fact  in  nature,  and  pointed  out  the 
character  of  its  operations  in  modifying  the  combinations 
of  material  agencies.  That  the  will  itself  is  subject  to 
its  own  laws  we  do  not  for  a  moment  deny ;  but  that  it 
is  *  controlled  by  its  antecedents,'  in  Professor  Tyndall's 
language,  we  are  very  far  from  admitting.  To  whatever 


370  FKAGMENTS   OP    SCIENCE. 

degree  its  acts  may  be  affected  by  its  own  past  history,  or 
by  the  influence  of  the  past  and  present  knowledge  pos- 
sessed by  the  understanding,  the  existence  of  an  apparent 
real  freedom  in  the  will  is  unquestionably  a  fact.  What- 
ever be  the  ultimate  character  of  this  freedom,  we  all  of 
us  think  we  are  free,  and  we  act  as  if  we  are  free.  Not, 
indeed,  that  we  act  as  if  our  freedom  were  absolute.  Our 
freedom  is  restrained  within  certain  limits.  It  is  limited 
by  the  laws  of  our  personal  character,  by  the  habits 
of  our  past  life,  and  in  one  man  it  appears  to  be  far 
stronger  and  more  independent  than  in  another.  But 
whether  it  is  by  the  exercise  of  a  certain  real  freedom  of 
the  will  that  we  ventilate  our  houses  and  take  other  pre- 
cautions against  contagion,  or  whether  this  freedom  is  a 
mere  deception  under  which  human  nature  labours,  so 
that  we  have  no  real  choice  as  to  what  we  will  or  will 
not  do — just  as  the  wheels  of  a  locomotive  cannot  help 
being  whirled  round  and  round  by  the  force  of  steam — the 
physical  results  are  the  same.  And  our  argument  as  to 
these  appointed  prayers  was  based  on  this  simple  pheno- 
menon in  the  organic  life  of  the  mental  and  material 
universe.  Just  so  far  as  a  man  possesses  an  immediate 
power  over  the  combinations  of  material  law,  just  so  far 
it  is  possible  that  he  may  be  able  to  influence  the  actual 
operations  of  law  by  the  entreaties  he  addresses  to  the 
Supreme  Authority  of  the  universe.  We  can  do  much 
ourselves  ;  and  there  is  no  absurdity  in  holding  that  it  is 
not  impossible  that  we  may  do  still  more  through  the 
agency  of  these  prayers. 

The  second  paragraph  of  Professor  Tyndall's  letter 
still  further  suggests  the  suspicion  that  he  has  not  fully 
entered  into  the  view  we  put  forward.  The  theory,  he 
says,  would  apply  equally  well  to  the  beliefs  of  ancient 
heathens  and  modern  savages,  who  saw  and  see  in  almost 
every  change  of  the  aspects  of  Nature  the  hand  of  an 


REFLECTIONS   ON   PRAYER  AND   NATURAL   LAW.      371 

arbitrary  Deity  ;  and  it  justifies  equally  the  mildest  and 
the  most  extravagant  belief  in  spontaneous  interferences. 
By  what  possible  reasoning  process  are  these  inferences 
extracted  from  our  statements  ?  How  does  the  belief 
that  some  results  may  possibly  be  effected  by  the  agency 
of  prayer  lead  to  the  conclusion  that  we  may  invariably 
expect  results  of  gigantic  magnitude?  What,  let  us  ask, 
are  the  results  of  all  human  action  upon  the  physical  laws 
of  the  universe  ?  For  one  successful  result  of  our  efforts 
are  we  not  baffled  a  thousand  times?  It  is  said  that 
praying  is  logically  absurd,  because  it  is  like  shooting  an 
arrow  into  the  dark.  Nobody  knows,  and  nobody  can 
know,  whether  it  really  does  any  good.  But  is  not  the 
same  to  be  said  of  almost  everything  we  attempt  ?  What 
has  been  the  result  of  all  our  speculations  as  to  the  cause 
and  nature  of  cholera,  and  as  to  the  remedies  to  which  it 
will  yield  ?  Nothing,  or  almost  nothing.  We  have  shot 
our  arrows  into  the  dark,  and  know  not  where  they  have 
fallen.  But  is  that  a  reason  for  discontinuing  our 
speculations  and  experiments  ?  Far  from  it.  How  many 
thousand  years  have  doctors  been  trying  to  cure  diseases 
of  all  kinds  ?  And  yet,  to  this  day,  what  do  they  know, 
and  what  can  they  do  ?  Are  there  yet  as  many  as  half  a 
dozen  really  proved  '  specifics '  for  as  many  complaints  ? 
Yet  they  continue  their  guessings  and  experimentalisings, 
and  wisely  continue  them.  The  heathen  and  modern 
savage  knew  and  know  little  or  nothing  of  the  nature  of 
law,  as  such  ;  but  how  does  that  affect  our  argument, 
which  is  grounded  on  the  recognition  of  the  absolute 
supremacy  of  all  law?  They  held  and  hold  that  the 
Eternal  Mind  acts  on  caprice,  and  '  spontaneously  inter- 
feres 'in  the  government  of  the  world.  How  does  that 
error  dispose  of  a  theory  which  rests  on  the  hypothesis 
that  (rod  never  acts  on  caprice,  and  which  simply  suggests 
the  possibility  of  an  extension  of  the  laws  of  human  action 


872  FRAGMENTS   OF   SCIENCE. 

into  a  sphere  where  the  mind  can  penetrate,  though  the 
hand  and  the  eye  are  restrained  from  following  it  ?  '  You 
will  admit,'  says  Mr.  Tyndall,  '  that  prayer,  as  a  preven- 
tive or  remedial  agent,  in  the  case  of  the  small-pox,  proved 
no  match  for  vaccination.'  We  reply,  that  we  never 
contrasted  them.  There  never  was  a  race  between  the 
two.  Vaccination  we  now  know  to  be  a  most  efficacious 
preventive ;  but  how  does  that  prove  that  prayer  is 
necessarily  inoperative  ?  For  thousands  of  years  man- 
kind knew  nothing  of  the  value  of  vaccination.  On  Mr. 
Tyndall's  theory  of  reasoning,  it  might  be  alleged  that 
the  ignorance  of  past  ages  proved  that  no  remedy  could 
possibly,  in  the  nature  of  things,  exist  at  all.  '  Would 
the  suppliant  voice  of  a  whole  nation  have  atoned  for  the 
bad  engineering,  or  caused  a  suspension  of  the  laws  of 
hydraulic  pressure,  in  the  case  of  the  Bradfield  reservoir  ? ' 
Undoubtedly  not.  But  how  does  that  prove  that  there 
can  be  no  possible  combinations  of  physical  laws  except 
those  which  we  produce  with  our  arms  and  hands  ?  A 
Eed  Indian  might  with  equal  reason  conclude  that,  be- 
cause he  could  not  make  a  watch,  therefore  no  human 
being  could  make  one.  '  The  great  majority  of  sane  per- 
sons at  the  present  day,'  continues  Professor  Tyndall, 
4  believe  in  the  necessary  character  of  natural  laws,  and 
it  is  only  where  the  antecedents  of  a  calamity  are  vague 
or  disguised  that  they  think  of  resorting  to  prayer  to  avert 
it.'  Undeniably.  It  is  also  equally  true  that  the  great 
majority  of  sane  persons  do  not  think  of  resorting  to 
drainage  and  ventilation  until  the  cholera  has  shown  itself; 
but  their  folly  is  no  disproof  of  the  value  of  good  drains 
and  fresh  air.  The  popular  neglect  of  a  remedy  does  not 
prove  its  worthlessness ;  otherwise,  by  a  parity  of  reason- 
ing, the  popularity  of  a  quack  medicine  would  prove  its 
excellence,  and  Holloway's  Pills  would  be  the  one  infal- 
lible remedy  for  all  our  ills.  The  theory  we  have 


REFLECTIONS    ON  PRAYEE   AND   NATURAL   LAW.      373 

attempted,  however  feebly,  to  explain,  undoubtedly  applies 
to  every  circumstance  of  human  life.  If  prayer  is  the 
supplement  to  the  labours  of  our  hands,  and  completes 
the  organic  harmony  of  the  entire  universe,  unquestion- 
ably it  is  absurd  to  have  recourse  to  it  only  when  we  are 
smitten  with  a  national  panic. 

Here,  indeed,  is  the  ground  for  an  objection  to  these 
national  acts  of  supplication.  If  the  Privy  Council  tell 
us  to  pray  because  the  cholera  is  advancing  from  east  to 
west,  do  they  not  encourage  the  notion  that  only  great 
calamities  come  from  God,  and  that  He  is  a  sort  of 
intruder  in  our  proper  domain,  which  in  ordinary 
seasons  He  leaves  altogether  to  our  own  management? 
We  do  not  say  that  this  is  an  objection  which  cannot  be 
satisfactorily  answered.  Nevertheless,  just  as  Sabbatarian 
rigorism  tends  to  promote  week-day  godlessness,  so  these 
panic-stricken  supplications  have  a  tendency  to  foster 
that  epicureanism  in  theology  to  which  we  are  all  of  us 
sufficiently  disposed. 

When  the  devil  was  sick,  the  devil  a  saint  would  be ; 
When  the  devil  got  well,  the  devil  a  saint  was  he. 


To  this  article  I  replied  on  the  19th  in  the  following 
terms  : — 

To  the  EDITOB  of  the  '  PALL  MALT,  GAZETTE.' 

SIR, — I  have  read  with  interest  the  letters  of  your  corre- 
spondents ;  E.  W.'  and '  H.  W.  W.,'  and  your  own  thoughtful 
second  article  on  the  influence  of  national  prayer.  It  gives 
me  true  pleasure  to  exchange  ideas  with  such  earnest  men 
on  so  important  a  subject. 

In  answer  to  your  correspondent  '  E.  W.'  I  would  first 
gay  that  when  I  affirm  necessity  I  merely  affirm  the  result 


874  FRAGMENTS   OF   SCIENCE. 

of  knowledge  and  experience.  Science  shows  that  certain 
consequents  follow  certain  antecedents  with  such  undeviat- 
ing  uniformity  that  the  association  between  antecedent 
and  consequent  has  become  inseparable  in  thought.  We 
explain  the  known  and  predict  the  unknown  on  the  as- 
sumption of  this  inseparability.  On  the  same  ground  of 
experience,  the  ideas  of  prayer  and  of  a  change  in  the 
course  of  natural  phenomena  refuse  to  be  connected  in 
thought.  I  believe  that  water  will  wet,  that  iron  will 
sink  in  it,  that  fire  will  burn,  that  the  sun  will  rise  to- 
morrow, and  hold  that  no  prayer  at  the  present  day  will 
alter  such  facts.  Both  you  and  your  correspondents  prob- 
ably entertain  the  same  opinion.  You  do  not  seem 
disposed  to  pray  for  undoubted  miracles.  Where  the 
antecedent  is  perfectly  clear,  you  prepare  yourselves  for 
the  consequent.  Now,  as  a  matter  of  fact,  in  cases  of 
national  supplication  the  antecedents  are  often  very  clear 
to  one  class  of  the  community,  though  very  dark  to 
another  and  a  larger  class.  This  explains  the  fact,  that 
while  the  latter  are  ready  to  resort  to  prayer,  the  former 
decline  doing  so.  The  difference  between  both  classes  is 
one  of  knowledge,  not  of  religious  feeling.  I  turn  to  the 
account  of  the  Epping  cholera  case,  and  learn  that  the 
people  drank  poisoned  water.  To  alter,  by  prayer,  the 
consequences  of  this  or  any  similar  fact — to  deprive,  by 
petition,  even  a  single  molecule  of  miasmatic  matter  of  its 
properties — would  in  the  eye  of  science  be  as  much  a 
miracle  as  to  make  the  sun  and  moon  stand  still.  For 
one  of  these  results  neither  of  us  would  pray ;  on  the  same 
grounds  I  refuse  to  pray  for  either. 

With  regard  to  the  efficacy  of  prayer,  I  grant  all 
manner  of  possibilities,  or,  more  correctly,  conceivabilities. 
Whenever  we  have  undoubted  evidence  of  the  smallest 
phenomenon,  we  can,  in  imagination,  expand  it  to  the 
largest.  I  jump  over  a  hillock,  and  can  therefore  imagine 


REFLECTIONS   ON  PRAYER  AND   NATURAL   LAW.      375 

a  man  jumping  over  Mont  Blanc.  Certain  bodies  are 
repelled  by  the  poles  of  a  magnet,  and  I  can  imagine  this 
force  of  repulsion  so  augmented  as  to  urge  projectiles  in 
war.  But  though  I  can  conceive  both,  I  believe  in  neither 
the  jumping  of  the  mountain  nor  the  projectile  force  of 
diamagnetism.  Similarly,  a  good-natured  man  grants  my 
request  when  I  ask  him  for  a  share  of  his  umbrella.  I 
can,  in  imagination,  expand  this  fact  to  the  infinite,  and 
ask  Omnipotence  to  ward  off  the  rain  from  my  paddock. 
That  He  may  do  so  is  conceivable,  but  experience  renders 
it  unbelievable.  The  people  of  England  are  already  more 
or  less  conscious  of  this  ;  and  the  practice  of  national 
propitiation  is,  I  believe,  doomed,  which  requires  the  great 
ability  of  this  journal — not  to  direct  the  spontaneous 
fervour  of  a  smitten  and  a  threatened  people  to  the  Throne 
of  Grace — not  even  to  prove  that  it  is  the  bounden  duty  of 
the  nation  to  engage  in  supplication — but  to  show  that 
such  an  act  is  not  intrinsically  absurd. 

Both  your  correspondents  seem  to  think  that  scien- 
tific discovery  may  be  a  result  of  a  prayer.  If  this  be 
believed,  I  will  only  say  that  the  bearing  of  theology 
towards  science  at  the  present  day  is  as  unpardonable  as 
it  is  unaccountable. 

You  speak  very  frequently  of  the  combinations  of 
material  law  possible  to  man.  Have  you  ever  analysed 
these  combinations  ?  You  stretch  forth  your  arm  and 
move  your  inkstand.  Is  this  an  act  of  volition  pure  and 
simple?  It  is  not.  The  external  motion  of  your  arm  is 
derived  immediately  from  a  motion  within  your  arm — it 
is,  in  fact,  this  motion  in  another  shape.  While  you  were 
pushing  your  inkstand  a  certain  amount  of  oxidation 
occurred  in  the  muscles  of  your  arm,  which  oxidation, 
under  normal  circumstances,  produces  a  certain  definite 
amount  of  heat.  To  move  the  inkstand,  a  quantity  of 
that  heat  has  been  consumed,  which  is  the  exact  thermal 


376  FKAGMENTS   OF   SCIENCE. 

equivalent  of  the  work  done.  You  could  do  the  same 
work  with  the  same  amount  of  heat  from  an  ordinary  fire. 
The  force  employed  is  the  force  of  your  food  which  is 
stored  up  in  your  muscles.  The  motor  nerves  pull  the 
trigger  and  discharge  this  force.  You  have  here  a  series 
of  transformations  of  purely  physical  energy  with  one 
critical  point  involved  in  the  question,  '  What  causes  the 
motor  nerves  to  pull  the  trigger  ? '  Is  the  cause  physical 
or  super-physical  ?  Is  it  a  sound  or  a  gleam,  or  an  ex- 
ternal prick  or  pressure,  or  some  internal  uneasiness  that 
stimulates  the  nerves  to  unlock  the  muscular  force,  or  is 
it  free  will  ?  Whatever  the  true  answer  to  the  question 
may  be,  your  safety  consists  in  affirming  boldly  that  free 
will  must  be  the  cause  of  the  nervous  action.  But  this, 
your  only  line  of  retreat,  you  have  deliberately  closed  by 
saying  that,  whether  the  will  is  free  or  not,  '  the  physical 
results  are  the  same.'  By  thus  dispensing  with  free  will 
you  cause  human  actions  to  take  their  place  in  the  chain 
of  physical  sequence,  and  human  combinations  of  material 
laws  no  more  justify  your  conclusions  regarding  prayer  to 
a  free  Deity  than  does  the  combination  of  the  molecules 
of  water  to  form  frost-flowers  upon  your  window-pane. 

Finally,  I  object  to  any  philosophy,  or  theology,  which 
selects  a  special  series  of  natural  phenomena  as  the  sub- 
ject of  national  supplication,  and  shrinks  from  the  same 
act  with  reference  to  other  phenomena.  In  reply  to  my 
question  whether  the  suppliant  voice  of  a  whole  nation 
would  have  altered  the  laws  of  hydraulic  pressure  in  the 
case  of  the  Bradfield  reservoir,  you  reply,  '  Undoubtedly 
not.'  Why  not  ?  I  would  earnestly  ask.  You  advocate 
prayers  for  fair  weather  and  for  rain.  Now  the  absence 
or  presence  of  rain  depends  upon  laws  of  gaseous  pressure 
which  are  just  as  immutable  as  those  of  water  pressure  ; 
and  the  only  reason  that  I  can  see  for  the  assumption 
that  the  one  is  the  object  of  Divine  interference,  and  the 


REFLECTIONS  ON  PRAYER  AND  NATURAL  LAW.   377 

other  not,  is  that  one  of  them  is  770  times  heavier  than 
the  other.  Your  position  puts  one  in  mind  of  the  remark 
of  Galileo,  that  Nature  abhorred  a  vacuum  only  to  a 
height  of  thirty-two  feet.  '  Divine  intervention  is  think- 
able,' you  virtually  say,  '  but  only  in  the  case  of  bodies  of 
small  specific  gravity.'  '  Stupendous  interferences,'  or 
'  results  of  gigantic  magnitude,'  are  not  to  be  expected, 
but  small  shiftings  reasonably  may.  Again  I  ask  you,  in 
all  earnestness,  How  came  you  to  know  this  ?  To  me  it 
appears  that  you  are  unwittingly  taking  dangerous  liber- 
ties with  the  established  laws  of  the  universe.  These 
laws  abolish  your  distinctions  of  large  and  small,  and  make 
it  as  great  a  miracle  to  suspend  the  gravity  of  a  straw  as 
to  extinguish  the  force  which  holds  the  solar  system 
together. 

With  these  remarks,  and  with  thanks  to  you  for  the 
opportunity  of  making  them,  I  would  willingly  refer  the 
final  adjudication  of  the  case  between  us  to  the  coming 
time. — Your  obedient  servant, 

JOHN  TYNDALL. 


Immediately  afterwards  the  editor  thus  closed  the 
discussion : — 

The  very  number  and  variety  of  the  letters  we  have 
received  on  the  subject  of  prayer  incline  us  to  favour  the 
suggestion  of  our  able  correspondent  '  M.  J.  H.,'  and  end, 
or  suspend,  the  controversy.  We  confess  to  a  lurking 
feeling  of  regret  at  doing  so,  for  nothing  more  important 
than  the  efficacy  of  prayer  can  occupy  the  minds  of  men, 
and  much  is  to  be  hoped  from  any  controversy  in  which 
intellects  so  clear,  so  consistent,  so  courageous  as  Professor 
Tyndall's  have  part.  But  in  all  the  many  able  letters 
before  us  we  find  nothing  that  really  brings  us  nearer  to 


878  FRAGMENTS    OF   SCIENCE. 

a  solution  of  our  difficulties.  In  some,  our  own  suggestion 
is  supported — in  others  Professor  Tyndall's  broad  and 
bold  argument  is  backed ;  but  nothing  new  is  added  to 
either.  We  leave  them,  then,  to  bear  what  fruit  they  may, 
without  adding  to  the  discussion  what  would  only  lead  to  a 
mere  multiplication  of  words.  Enough  has  been  said,  at 
present,  for  candid  and  thoughtful  men.  Nobody  can  mis- 
take Professor  Tyndall's  line  of  argument — he  himself  pro- 
bably could  not  make  it  clearer ;  while,  as  for  ourselves,  we 
do  not  presume  to  dogmatise  upon  such  questions,  but  we 
still  believe  all  that  we  stated,  and  for  the  considerations  we 
stated,  in  the  beginning  of  the  discussion — namely,  that 
to  pray  for  the  abatement  of  pestilence  is  not  philo- 
sophically absurd. 


These  are  the  simple  historic  antecedents  of  the  follow- 
ing series  of  articles. 


n. 

MIRACLES  AND  SPECIAL  PROVIDENCES* 

18G7. 

IT  is  my  privilege  to  enjoy  the  friendship  of  a  select 
number  of  religious  men,  with  whom  I  converse  frankly 
upon  theological  subjects,  expressing  without  disguise  the 
notions  and  opinions  I  entertain  regarding  their  tenets, 
and  hearing  in  return  these  notions  and  opinions  subjected 
to  criticism.  I  have  thus  far  found  them  liberal  and 
loving  men,  patient  in  hearing,  tolerant  in  reply,  who 
know  how  to  reconcile  the  duties  of  courtesy  with  the 
earnestness  of  debate.  From  one  of  these,  nearly  a  year 
ago,  I  received  a  note,  recommending  strongly  to  my  at- 
tention the  volume  of  'Bampton  Lectures'  for  1865,  in 
which  the  question  of  miracles  is  treated  by  Mr.  Mozley. 
Previous  to  receiving  this  note,  I  had  in  part  made  the 
acquaintance  of  the  work  through  an  able  and  elaborate 
review  of  it  in  the  '  Times.'  The  combined  effect  of  the 
letter  and  the  review  was  to  make  the  book  the  companion 
of  my  summer  tour  in  the  Alps.  There,  during  the  wet 
and  snowy  days  which  were  only  too  prevalent  in  1866, 
and  during  the  days  of  rest  interpolated  between  days  of 
toil,  I  made  myself  more  thoroughly  conversant  with  Mr. 
Mozley's  volume.  I  found  it  clear  and  strong — an  intel- 
lectual tonic,  as  bracing  and  pleasant  to  my  mind  as  the 
seen  air  of  the  mountains  was  to  my  body.  From  time 

1  '  Fortnightly  Eeriew,'  New  Series,  vol.  i.  p.  645. 


880  FRAGMENTS    OF   SCIENCE. 

to  time  I  jotted  down  thoughts  regarding  it,  intending 
afterwards,  if  time  permitted,  to  work  them  up  into  a  co- 
herent whole.  Other  duties,  however,  interfered  with  the 
complete  carrying  out  of  this  intention,  and  what  I  wrote 
last  summer  I  now  publish,  not  hoping  to  be  able,  within 
any  reasonable  time,  to  render  my  defence  of  scientific 
method  more  complete. 

Mr.  Mozley  refers  at  the  outset  of  his  task  to  the 
movement  against  miracles  which  of  late  years  has  taken 
place,  and  which  determined  his  choice  of  a  subject.  He 
acquits  modern  science  of  having  had  any  great  share  in 
the  production  of  this  movement.  The  objection  against 
miracles,  he  says,  does  not  arise  from  any  minute  know- 
ledge of  the  laws  of  nature,  but  simply  because  they  are 
opposed  to  that  plain  and  obvious  order  of  nature  which 
everybody  sees.  The  present  movement  is,  he  thinks,  to 
be  ascribed  to  the  greater  earnestness  and  penetration  of 
the  present  age.  Formerly  miracles  were  accepted  with- 
out question,  because  without  reflection ;  but  the  exercise 
of  what  Mr.  Mozley  calls  the  historic  imagination  is  a 
characteristic  of  our  own  time.  Men  are  now  accustomed 
to  place  before  themselves  vivid  images  of  historic  facts  ; 
and  when  a  miracle  rises  to  view,  they  halt  before  the 
astounding  occurrence,  and,  realising  it  with  the  same 
clearness  as  if  it  were  now  passing  before  their  eyes,  they 
ask  themselves,  t  Can  this  have  taken  place  ?  '  In  some 
instances  the  effort  to  answer  this  question  has  led  to  a 
disbelief  in  miracles,  in  others  to  a  strengthening  of  belief. 
The  end  and  aim  of  Mr.  Mozley's  lectures  is  to  show  that 
the  strengthening  of  belief  is  the  logical  result  which 
ought  to  follow  from  the  examination  of  the  facts. 

Attempts  have  been  made  by  religious  men  to  bring 
the  Scripture  miracles  within  the  scope  of  the  order  of 
nature,  but  all  such  attempts  are  rejected  by  Mr.  Mozley 
as  utterly  futile  and  wide  of  the  mark.  Regarding  miracles 


MIRACLES   AND    SPECIAL   PROVIDENCES.  381 

as  a  necessary  accompaniment  of  a  revelation,  their  evi- 
dential value  in  his  eyes  depends  entirely  upon  their  de- 
viation from  the  order  of  nature.  Thus  deviating,  they 
suggest  and  illustrate  a  power  higher  than  nature,  a 
*  personal  will ; '  and  they  commend  the  person  in  whom 
this  power  is  vested  as  a  messenger  from  on  high.  With" 
out  these  credentials  such  a  messenger  would  have  no 
right  to  demand  helief,  even  were  his  assertions  regarding 
his  Divine  mission  backed  by  a  holy  life.  Nor  is  it  by 
miracles  alone  that  the  order  of  nature  is,  or  may  be,  dis- 
turbed. The  material  universe  is  also  the  arena  of 
'  special  providences.'  Under  these  two  heads  Mr.  Mozley 
distributes  the  total  preternatural.  One  form  of  the 
preternatural  may  shade  into  the  other,  as  one  colour 
passes  into  another  in  the  rainbow;  but,  while  the  line 
which  divides  the  specially  providential  from  the  miracu- 
lous cannot  be  sharply  drawn,  their  distinction  broadly 
expressed  is  this :  that,  while  a  special  providence  can  only 
excite  surmise  more  or  less  probable,  it  is  '  the  nature  of 
a  miracle  to  give  proof,  as  distinguished  from  mere  sur- 
mise, of  Divine  design.' 

Mr.  Mozley  adduces  various  illustrations  of  what  he 
regards  to  be  special  providences,  as  distinguished  from 
miracles.  '  The  death  of  Arius,'  he  says,  '  was  not  mira- 
culous, because  the  coincidence  of  the  death  of  a  here- 
siarch  taking  place  when  it  was  peculiarly  advantageous 
to  the  orthodox  faith  ....  was  not  such  as  to  compel 
the  inference  of  extraordinary  Divine  agency ;  but  it  was 
a  special  providence,  because  it  carried  a  reasonable  ap- 
pearance of  it.  The  miracle  of  the  Thundering  Legion 
was  a  special  providence,  but  not  a  miracle,  for  the  same 
reason,  because  the  coincidence  of  an  instantaneous  fall 
of  rain,  in  answer  to  prayer,  carried  some  appearance,  but 
not  proof,  of  preternatural  agency.'  The  eminent  lecturer's 
remarks  on  this  head  brought  to  my  recollection  certain 


882  FRAGMENTS    OF   SCIENCE. 

narratives  published  in  Methodist  magazines,  which  I 
used  to  read  with  avidity  when  a  boy.  The  title  of  these 
exciting  stories,  if  I  remember  right,  was  '  The  Provi- 
dence of  God  asserted,'  and  in  them  the  most  extra- 
ordinary escapes  from  peril  were  recounted  and  ascribed 
to  prayer,  while  equally  wonderful  instances  of  calamity 
were  adduced  as  illustrations  of  Divine  retribution.  In 
such  magazines,  or  elsewhere,  I  found  recorded  the  case 
of  the  celebrated  Samuel  Hick,  which,  as  it  illustrates  a 
whole  class  of  special  providences  approaching  in  con- 
clusiveness  to  miracles,  is  worthy  of  mention  here.  It  is 
related  of  this  holy  man — and  I,  for  one,  have  no  doubt 
of  his  holiness — that  flour  was  lacking  to  make  the  sacra- 
mental bread.  Grain  was  present,  and  a  windmill  was 
present,  but  there  was  no  wind  to  grind  the  corn.  With 
faith  undoubting,  Samuel  Hick  prayed  to  the  Lord  of  the 
winds  :  the  sails  turned,  the  corn  was  ground,  after  which 
the  wind  ceased.  According  to  the  canon  of  the  Bampton 
Lecturer,  this,  though  carrying  a  strong  appearance  of  an 
immediate  exertion  of  Divine  energy,  lacks  by  a  hair's- 
breadth  the  quality  of  a  miracle.  For  the  wind  might 
have  arisen,  and  might  have  ceased,  in  the  ordinary 
course  of  nature.  Hence  the  occurrence  did  not '  compel 
the  inference  of  extraordinary  Divine  agency.'  In  like 
manner  Mr.  Mozley  considers  that  'the  appearance  of 
the  cross  to  Constantine  was  a  miracle,  or  a  special  pro- 
vidence, according  to  which  account  of  it  we  adopt.  As 
only  a  meteoric  appearance  in  the  shape  of  a  cross  it 
gave  some  token  of  preternatural  agency,  but  not  full 
evidence.' 

In  the  Catholic  canton  of  Switzerland  where  I  now 
write,  and  still  more  among  the  pious  Tyrolese,  the  moun- 
tains are  dotted  with  shrines,  containing  offerings  of  all 
kinds,  in  acknowledgment  of  special  mercies — legs,  feet, 
arms,  and  hands — of  gold,  silver,  brass,  and  wood,  according 


MIRACLES   AND   SPECIAL  PROVIDENCES.  883 

as  worldly  possessions  enabled  the  grateful  heart  to  ex- 
press its  indebtedness.  Most  of  these  offerings  are  made 
to  the  Virgin  Mary.  They  are  recognitions  of  '  special 
providences,'  wrought  through  the  instrumentality  of  the 
Mother  of  God.  Mr.  Mozley's  belief,  that  of  the  Methodist 
chronicler,  and  that  of  the  Tyrolese  peasant,  are  sub- 
stantially the  same.  Each  of  them  assumes  that  nature, 
instead  of  flowing  ever  onward  in  the  uninterrupted  rhythir 
of  cause  and  effect,  is  mediately  ruled  by  the  free  human 
will.  As  regards  direct  action  upon  natural  phenomena, 
man's  will  is  confessedly  powerless  ;  but  it  is  the  triggei 
•which,  by  its  own  free  action,  liberates  the  Divine 
power.  In  this  sense,  and  to  this  extent,  man,  of  course, 
commands  nature. 

Did  the  existence  of  this  belief  depend  solely  upon 
the  material  benefits  derived  from  it,  it  could  not,  in  my 
opinion,  last  a  decade.  As  a  purely  objective  fact,  we 
should  soon  see  that  the  distribution  of  natural  pheno- 
mena is  unaffected  by  the  merits  or  the  demerits  of  men ; 
that  the  law  of  gravitation  crushes  the  simple  worshippers 
of  Ottery  St.  Mary,  while  singing  their  hymns,  just  as 
surely  as  if  they  were  engaged  in  a  midnight  brawl.  The 
hold  of  this  belief  upon  the  human  mind  is  not  due  to 
outward  verification,  but  to  the  inner  warmth,  force,  and 
elevation  with  which  it  is  commonly  associated.  It  is 
plain,  however,  that  these  feelings  may  exist  under  the 
most  various  forms.  They  are  not  limited  to  Church  of 
England  Protestantism — they  are  not  even  limited  to 
Christianity.  Though  less  refined,  they  are  certainly  not 
less  strong  in  the  heart  of  the  Methodist  and  the  Tyrolese 
peasant  than  in  the  heart  of  Mr.  Mozley.  Indeed,  those 
feelings  belong  to  the  primal  powers  of  man's  nature.  A 
*  sceptic '  may  have  them.  They  find  vent  in  the  battle- 
cry  of  the  Moslem.  They  take  hue  and  form  in  the 
hunting-grounds  of  the  red  Indian  ;  and  raise  all  of  them, 


884  FEAGMEISTS    OF   SCIENCE. 

as  they  raise  the  Christian,  upon  a  wave  of  victory,  above 
the  ten  ors  of  the  grave. 

The  character,  then,  of  a  miracle,  as  distinguished 
from  a  special  providence,  is  that  the  former  furnishes 
proof,  while  in  the  case  of  the  latter  we  have  only  sur- 
mise. Dissolve  the  element  of  doubt,  and  the  alleged 
fact  passes  from  the  one  class  of  the  preternatural  into 
the  other.  In  other  words,  if  a  special  providence  could 
be  proved  to  be  a  special  providence,  it  would  cease  to 
be  a  special  providence  and  become  a  miracle.  There  is 
not  the  least  cloudiness  about  Mr.  Mozley's  meaning  here. 
A  special  providence  is  a  doubtful  miracle.  Why,  then, 
not  call  it  so  ?  The  term  employed  by  Mr.  Mozley  conveys 
no  negative  suggestion,  whereas  the  negation  of  certainty 
is  the  peculiar  characteristic  of  the  thing  intended  to 
be  expressed.  There  is  an  apparent  unwillingness  on  the 
part  of  the  lecturer  to  call  a  special  providence  what  his 
own  definition  makes  it  to  be.  Instead  of  speaking 
of  it  as  a  doubtful  miracle,  he  calls  it  '  an  invisible 
miracle.'  He  speaks  of  the  point  of  contact  of  super- 
natural power  with  the  chain  of  causation  being  so  high 
up  as  to  be  wholly,  or  in  part,  out  of  sight,  whereas  the 
essence  of  a  special  providence  is  the  uncertainty  whether 
there  is  any  contact  at  all,  either  high  or  low.  By  the 
use  of  an  incorrect  term,  however,  a  grave  danger  is 
avoided.  For  the  idea  of  doubt,  if  kept  systematically  be- 
fore the  mind,  would  soon  be  fatal  to  the  special  providence, 
considered  as  a  means  of  edification.  The  term  employed, 
on  the  contrary,  invites  and  encourages  the  trust  which  is 
necessary  to  supplement  the  evidence. 

This  inner  trust,  though  at  first  rejected  by  Mr. 
Mozley  in  favour  of  external  proof,  is  subsequently  called 
upon  to  do  momentous  duty  in  regard  to  miracles.  When- 
ever the  evidence  of  tho  miraculous  seems  incommen- 
surate with  the  fact  which  it  has  to  establish,  or  rather 


MIRACLES    AND   SPECIAL   PROVIDENCES.  385 

when  the  fact  is  so  amazing  that  hardly  any  evidence  is 
sufficient  to  establish  it,  Mr.  Mozley  invokes  '  the  affec- 
tions.' They  must  urge  the  reason  to  accept  the  con- 
clusion, from  which  unaided  it  recoils.  The  affections 
and  emotions  are  eminently  the  court  of  appeal  in  matters 
of  real  religion,  which  is  an  affair  of  the  heart ;  but  they 
are  not,  I  submit,  the  court  in  which  to  weigh  allegations 
regarding  the  credibility  of  physical  facts.  These  must 
be  judged  by  the  dry  light  of  the  intellect  alone,  appeals 
to  the  affections  being  reserved  for  cases  where  moral 
elevation,  and  not  historic  conviction,. is  the  aim.  It  is, 
moreover,  because  the  result,  in  the  case  under  considera- 
tion, is  deemed  desirable  that  the  affections  are  called 
upon  to  back  it.  If  undesirable,  they  would,  with  equal 
right,  be  called  upon  to  act  the  other  way.  Even  to  the 
disciplined  scientific  mind  this  would  be  a  dangerous 
doctrine.  A  favourite  theory — the  desire  to  establish  or 
avoid  a  certain  result — can  so  warp  the  mind  as  to  destroy 
its  powers  of  estimating  facts.  I  have  known  men  to 
work  for  years  under  a  fascination  of  this  kind,  unable 
to  extricate  themselves  from  its  fatal  influence.  They 
had  certain  data,  but  not,  as  it  happened,  enough.  By  a 
process  exactly  analogous  to  that  invoked  by  Mr.  Moz- 
ley they  supplemented  the  data,  and  went  wrong.  From 
that  hour  their  intellects  were  so  blinded  to  the  percep- 
tion of  adverse,  phenomena  that  they  never  reached  truth. 
If,  then,  to  the  disciplined  scientific  mind,  this  incon- 
gruous mixture  of  proof  and  trust  be  fraught  with  danger, 
what  must  it  be  to  the  indiscriminate  audience  which  Mr. 
Mozley  addresses  ?  In  calling  upon  this  agency  he  acts 
the  part  of  Frankenstein.  It  is  a  monster  thus  evoked 
that  we  see  stalking  abroad,  in  the  degrading  spiritualistic 
phenomena  of  the  present  day.  Again,  I  say,  where  the 
aim  is  to  elevate  the  mind,  to  quicken  the  moral  sense, 
to  kindle  the  fire  of  religion  in  the  soul,  let  the  affections 


386  FKAGMENTS   OF   SCIENCE. 

by  all  means  be  invoked ;  but  they  must  not  be  per- 
mitted to  colour  our  reports,  or  to  influence  our  accept- 
ance of  reports  of  occurrences  in  external  nature.  Tes- 
timony as  to  natural  facts  is  worthless  when  wrapped 
in  this  atmosphere  of  the  affections ;  the  most  earnest 
subjective  truth  being  thus  rendered  perfectly  compatible 
with  the  most  astounding  objective  error. 

There  are  questions  in  judging  of  which  the  affections 
or  sympathies  are  often  our  best  guides,  the  estimation  of 
moral  goodness  being  one  of  these.  But  at  this  precise 
point,  where  they  are  really  of  use,  Mr.  Mozley  excludes 
the  affections  and  demands  a  miracle  as  a  certificate  of 
character.  He  will  not  accept  any  other  evidence  of  the 
perfect  goodness  of  Christ.  '  No  o/itward  life  or  conduct,' 
he  says,  '  however  irreproachable,  could  prove  His  perfect 
sinlessness,  because  goodness  depends  upon  the  inward 
motive,  and  the  perfection  of  the  inward  motive  is 
not  proved  by  the  outward  act.'  But  surely  the  miracle 
is  an  outward  act,  and  to  pass  from  it  to  the  inner  motive 
imposes  a  greater  strain  upon  logic  than  that  involved 
in  our  ordinary  methods  of  estimating  men.  There  is, 
at  least,  moral  congruity  between  the  outward  goodness 
and  the  inner  life,  but  there  is  no  such  congruity  between 
the  miracle  and  the  life  within.  The  test  of  moral  good- 
ness laid  down  by  Mr.  Mozley  is  not  the  test  of  John,  who 
says,  '  He  that  doeth  righteousness  is  righteous ; '  nor  is 
it  the  test  of  Jesus  :  '  By  their  fruits  ye  shall  know  them  ; 
do  men  gather  grapes  of  thorns,  or  figs  of  thistles?' 
But  it  is  the  test  of  another  :  <  If  thou  be  the  Son  of  God, 
command  that  these  stones  be  made  bread.'  For  my  own 
part,  I  prefer  the  attitude  of  Fichte  to  that  of  Mr. 
Mozley.  '  The  Jesus  of  John,'  says  this  noble  and  mighty 
thinker,  'knows  no  other  God  than  the  True  God,  in 
whom  we  all  are,  and  live,  and  may  be  blessed,  and  out 
of  whom  there  is  only  Death  and  Nothingness.  And,' 


AIIKACLKS    A.ND    SPECIAL    PKOVlDilXCES.  387 

continues  Fichte,  '  he  appeals,  and  rightly  appeals,  in 
support  of  this  truth,  not  to  reasoning,  but  to  the  inward 
practical  sense  of  truth  in  man,  not  even  knowing  any 
other  proof  than  this  inward  testimony,  "  If  any  man  will 
do  the  will  of  Him  who  sent  Me,  he  shall  know  of  the 
doctrine  whether  it  be  of  God."' 

Accepting  Mr.  Mozley's  test,  with  which  alone  I  am 
now  dealing,  it  is  evident  that,  in  the  demonstration  of 
moral  goodness,  the  quantity  of  the  miraculous  comes  into 
play.  Had  Christ,  for  example,  limited  Himself  to  the 
conversion  of  water  into  wine,  He  would  have  fallen  short 
of  the  performance  of  Jannes  and  Jambres ;  for  it  is  a 
smaller  thing  to  convert  one  liquid  into  another  than  to 
convert  a  dead  rod  into  g  living  serpent.  But  Jannes  and 
Jambres,  we  are  informed,  were  not  good.  Hence,  if  Mr. 
Mozley's  test  be  a  true  one,  a  point  must  exist,  on  the  one 
side  of  which  miraculous  power  demonstrates  goodness, 
while  on  the  other  side  it  does  not.  How  is  this 
'  point  of  contrary  flexure '  to  be  determined  ?  It  must 
lie  somewhere  between  the  magicians  and  Moses,  for. 
within  this  space  the  power  passed  from  the  diabolical  to 
the  Divine.  But  how  to  mark  the  point  of  passage — how, 
out  of  a  purely  quantitative  difference  in  the  visible 
manifestation  of  power,  we  are  to  infer  a  total  inversion  of 
quality — it  is  extremely  difficult  to  see.  Moses,  we  are 
informed,  produced  a  large  reptile  ;  Jannes  and  Jambres 
produced  a  small  one.  I  do  not  possess  the  intellectual 
faculty  which  would  enable  me  to  infer,  from  those  data, 
either  the  goodness  of  the  one  or  the  badness  of  the 
other ;  and  in  the  highest  recorded  manifestations  of  the 
miraculous  I  am  equally  at  a  loss.  Let  us  not  play  fast 
and  loose  with  the  miraculous  ;  either  it  is  a  demonstra- 
tion of  goodness  in  all  cases  or  in  none.  If  Mr.  Mozley 
accepts  Christ's  goodness  as  transcendent,  because  He  did 
such  works  as  no  other  man  did,  he  ought,  logically 
19 


388  FRAGMENTS   OP   SCIENCE. 

speaking,  to  accept  the  works  of  those  who,  in  His  name, 
had  cast  out  devils,  as  demonstrating  a  proportionate 
goodness  on  their  part.  But  it  is  people  of  this  class  who 
are  consigned  to  everlasting  fire  prepared  for  the  devil 
and  his  angels.  Such  zeal  as  that  of  Mr.  Mozley  for 
miracles  tends,  I  fear,  to  eat  his  religion  up.  The  logical 
threatens  to  stifle  the  spiritual.  The  truly  religious  soul 
needs  no  miraculous  proof  of  the  goodness  of  Christ.  The 
words  addressed  to  Matthew  at  the  receipt  of  custom 
required  no  miracle  to  produce  obedience.  It  was  by  no 
stroke  of  the  supernatural  that  Jesus  caused  those  sent  to 
seize  Him  to  go  backward  and  fall  to  the  ground.  It  was 
the  sublime  and  holy  effluence  from  within,  which  needed 
no  prodigy  to  commend  it  to  the  reverence  even  of  his 
foes. 

As  regards  the  function  of  miracles  in  the  founding  of 
a  religion,  Mr.  Mozley  institutes  a  comparison  between 
the  religion  of  Christ  and  that  of  Mahomet ;  and  he  derides 
the  latter  as  '  irrational '  because  it  does  not  profess  to 
adduce  miracles  in  proof  of  its  supernatural  origin.  But 
the  religion  of  Mahomet,  notwithstanding  this  drawback, 
has  thriven  in  the  world,  and  at  one  time  it  held  sway 
over  larger  populations  than  Christianity  itself.  The 
spread  and  influence  of  Christianity  are,  however,  brought 
forward  by  Mr.  Mozley  as  '  a  permanent,  enormous,  and 
incalculable  practical  result '  of  Christian  miracles  ;  and 
he  makes  use  of  this  result  to  strengthen  his  plea  for 
the  miraculous.  His  logical  warrant  for  this  proceeding 
is  not  clear.  It  is  the  method  of  science,  when  a  phe- 
nomenon presents  itself,  towards  the  production  of  which 
several  elements  may  contribute,  to  exclude  them  one 
by  one,  so  as  to  arrive  at  length  at  the  truly  effec- 
tive cause.  Heat,  for  example,  is  associated  with  a  pheno- 
menon ;  we  exclude  heat,  but  the  phenomenon  remains : 
hence,  heat  is  not  its  cause.  Magnetism  is  associated 


MIEACLES   AND    SPECIAL   PROVIDENCES.  389 

with  a  phenomenon ;  we  exclude  magnetism,  but  the 
phenomenon  remains :  hence,  magnetism  is  not  its  cause. 
Thus,  also,  when  we  seek  the  cause  of  the  diffusion  of  a 
religion — whether  it  he  due  to  miracles,  or  to  the  spiritual 
force  of  its  founders — we  exclude  the  miracles,  and,  find- 
ing the  result  unchanged,  we  infer  that  miracles  are  not 
the  effective  cause.  This  important  experiment  Mahomet- 
anism  has  made  for  us.  It  has  lived  and  spread  without 
miracles ;  and  to  assert,  in  the  face  of  this,  that  Christi- 
anity has  spread  because  of  miracles,  is  not  more  opposed 
to  the  spirit  of  science  than  to  the  common  sense  of  man- 
kind. 

The  incongruity  of  inferring  moral  goodness  from 
miraculous  power  has  been  dwelt  upon  above ;  in  another 
particular  also  the  strain  put  by  Mr.  Mozley  upon  mira- 
cles is,  I  think,  more  than  they  can  bear.  In  consistency 
with  his  principles,  it  is  difficult  to  see  how  he  is  to  draw 
from  the  miracles  of  Christ  any  certain  conclusion  as  to 
His  Divine  nature.  He  dwells  very  forcibly  on  what  he 
calls  '  the  argument  from  experience,'  in  the  demolition  of 
which  he  takes  evident  delight.  He  destroys  the  argu- 
ment, and  repeats  it,  for  the  mere  pleasure  of  again  and 
again  knocking  the  breath  out  of  it.  Experience,  he 
urges,  can  only  deal  with  the  past ;  and  the  moment  we 
attempt  to  project  experience  a  hair's-breadth  beyond  the 
point  it  has  at  any  moment  reached,  we  are  condemned 
by  reason.  It  appears  to  me  that  when  he  infers  from 
Christ's  miracles  a  Divine  and  altogether  superhuman 
energy,  Mr.  Mozley  places  himself  precisely  under  this 
condemnation.  For  what  is  his  logical  ground  for  con- 
cluding that  the  miracles  of  the  New  Testament  illustrate 
Divine  power  ?  May  they  not  be  the  result  of  expanded 
human  power  ?  A  miracle  he  defines  as  something  im- 
possible to  man.  But  how  does  he  know  that  the  miracles 
of  the  New  Testament  are  impossible  to  man?  Seek 


890  FRAGMENTS   OF    SC1KNCK. 

OB  he  may,  he  has  absolutely  no  reason  to  adduce  save  thig 
—  that  man  has  never  hitherto  accomplished  such  things. 
But  does  the  fact  that  man  has  never  raised  the  dead 
prove  that  he  can  never  raise  the  dead  ?  'Assuredly  not,' 
must  be  Mr.  Mozley's  reply  ;  '  for  this  would  be  pushing 
experience  beyond  the  limit  it  has  now  reached — 
which  I  pronounce  unlawful.'  Then  a  period  may  come 
when  man  will  be  able  to  raise  the  dead.  If  this  be  con- 
ceded— and  I  do  not  see  how  Mr.  Mozley  can  avoid  the 
concession — it  destroys  the  necessity  of  inferring  Christ's 
Divinity  from  His  miracles.  He,  it  may  be  contended, 
antedated  the  humanity  of  the  future ;  as  a  mighty  tidal 
wave  leaves  high  upon  the  beach  a  mark  which  by-and-by 
becomes  the  general  level  of  the  ocean.  Turn  the  matter 
as  you  will,  no  other  warrant  will  be  found  for  the  all-im- 
portant conclusion  that  Christ's  miracles  demonstrate 
Divine  power,  than  an  argument  which  has  been  stigma- 
tised by  Mr.  Mozley  as  a  '  rope  of  sand ' — the  argument 
from  experience. 

The  learned  Bampton  Lecturer  would  be  in  this  posi- 
tion, even  had  he  seen  with  his  own  eyes  every  miracle 
recorded  in  the  New  Testament.  But  he  has  not  seen 
these  miracles ;  and  his  intellectual  plight  is  therefore 
worse.  He  accepts  these  miracles  on  testimony.  Why 
does  he  believe  that  testimony  ?  How  does  he  know  that 
it  is  not  delusion  ;  how  is  he  sure  that  it  is  not  even 
fraud  ?  He  will  answer,  that  the  writing  bears  the  marks 
of  sobriety  and  truth  ;  and  that  in  many  cases  the  bearers 
of  this  message  to  mankind  sealed  it  with  their  blood. 
Granted  with  all  my  heart ;  but  whence  the  value  of 
all  this  ?  Is  it  not  solely  derived  from  the  fact  that  men, 
as  we  know  them,  do  not  sacrifice  their  lives  in  the  attest- 
ation of  that  which  they  know  to  be  untrue  ?  Does  not 
the  entire  value  of  the  testimony  of  the  apostles  depend 
ultimately  upon  our  experience  of  human  nature  ?  Jt 


MIRACLES   AND    SPECIAL    PROVIDENCES.  391 

appears,  therefore,  that  those  said  to  have  seen  the 
miracles,  based  their  inferences  from  what  they  saw  on 
the  argument  from  experience ;  and  that  Mr.  Mozley 
bases  his  belief  in  their  testimony  on  the  same  argument. 
The  weakness  of  his  conclusion  is  quadrupled  by  this 
double  insertion  of  a  principle  of  belief,  to  which  he  flatly 
denies  rationality.  His  reasoning,  in  fact,  cuts  two  ways — 
if  it  destroys  our  trust  in  the  order  of  nature,  it  far  more 
effectually  abolishes  the  basis  on  which  Mr.  Mozley  seeks 
to  found  the  Christian  religion. 

Over  this  argument  from  experience,  which  at  bottom 
is  his  argument,  Mr.  Mozley  rides  rough-shod.  There 
is  a  dash  of  scorn  in  the  energy  with  which  he  tramples 
on  it.  Probably  some  previous  writer  had  made  too  nmch 
of  it,  and  thus  invited  his  powerful  assault.  Finding 
the  difficulty  of  belief  in  miracles  to  rise  from  their  being 
in  contradiction  to  the  order  of  nature,  he  sets  himself  to 
examine  the  grounds  of  our  belief  in  that  order.  With 
a  vigour  of  logic  rarely  equalled,  and  with  a  confidence 
in  its  conclusions  never  surpassed,  he  disposes  of  this 
belief  in  a  manner  calculated  to  startle  those  who,  with- 
out due  examination,  had  come  to  the  conclusion  that  the 
order  of  nature  was  secure. 

What  we  mean,  he  says,  by  our  belief  in  the  order  of 
nature,  is  the  belief  that  the  future  will  be  like  the  past. 
There  is  not,  according  to  Mr.  Mozley,  the  slightest 
rational  basis  for  this  belief. 

'  Tha.t  any  cause  in  nature  is  more  permanent  than  its  existing 
and  known  effects,  extending  further,  and  about  to  produce  other 
and  more  instances  besides  what  it  has  produced  already,  we  have 
no  evidence.  Let  us  imagine,'  he  continues,  '  the  occurrence  of  a 
particular  physical  phenomenon  for  the  first  time.  Upon  that 
Bingle  occurrence  we  should  have  but  the  very  faintest  expecta- 
tion of  another.  If  it  did  occur  again,  once  or  twice,  so  far  from 


892  FKAGMENTS   OF   SCIENCE. 

counting  on  another  occurrence,  a  cessation  would  occur  as  the 
most  natural  event  to  us.  But  let  it  continue  one  hundred  times, 
and  we  should  find  no  hesitation  in  inviting  persons  from  a 
distance  to  see  it;  and  if  it  occurred  every  day  for  years,  its 
occurrence  would  be  a  certainty  to  us,  its  cessation  a  marvel.  .  . 
What  ground  of  reason  can  we  assign  for  an  expectation  that  any 
part  of  the  course  of  nature  will  be  the  next  moment  what  it  has 
been  up  to  this  moment,  i.e.  for  our  belief  in  the  uniformity  of 
nature  ?  None.  No  demonstrative  reason  can  be  given,  for  the 
contrary  to  the  recurrence  of  a  fact  of  nature  is  no  contradiction. 
No  probable  reason  can  be  given ;  for  all  probable  reasoning  re- 
specting the  course  of  nature  is  founded  upon  this  presumption  of 
likeness,  and  therefore  cannot  be  the  foundation  of  it.  No  reason 
can  be  given  for  this  belief.  It  is  without  a  reason.  It  rests 
upon  no  rational  grounds,  and  can  be  traced  to  no  rational 
principle.' 

'  Everything,'  Mr.  Mozley,  however,  adds,  '  depends 
upon  this  belief,  every  provision  we  make  for  the  future, 
every  safeguard  and  caution  we  employ  against  it,  all 
calculation,  all  adjustment  of  means  to  ends  supposes  this 
belief ;  and  yet  this  belief  has  no  more  producible  reason 

for  it  than  a  speculation  of  fancy It  is  necessary, 

all-important  for  the  purposes  of  life,  but  solely  practical, 

and  possesses  no  intellectual  character The  proper 

function,'  continues  Mr.  Mozley,  '  of  the  inductive  prin- 
ciple, the  argument  from  experience,  the  belief  in  the 
order  of  nature — by  whatever  phrase  we  designate  the 
same  instinct — is  to  operate  as  a  practical  basis  for  the 
affairs  of  life  and  the  carrying  on  of  human  society.'  To 
sum  up,  the  belief  in  the  order  of  nature  is  general,  but  it 
is  'an  unintelligent  impulse,  of  which  we  can  give  no 
rational  account.'  It  is  inserted  into  our  constitution 
solely  to  induce  us  to  till  our  fields,  to  raise  our  winter  fuel, 
and  thus  to  meet  the  future  on  the  perfectly  gratuitous 
supposition  that  it  will  be  like  the  past. 

4  Thus  step  by  step,'  says  Mr.  Mozley,  with  the  emphasis 


MIRACLES   AND   SPECIAL   PROVIDENCES.  393 

of  a  man  who  feels  his  position  to  be  a  strong  one,  <  has 
philosophy  loosened  the  connection  of  the  order  of  nature 
with  the  ground  of  reason,  befriending  inexact  proportion 
as  it  has  done  this  the  principle  of  miracles.'  For  '  this 
belief  not  having  itself  a  foundation  in  reason,  the  ground 
is  gone  upon  which  it  could  be  maintained  that  miracles, 
as  opposed  to  the  order  of  nature,  are  opposed  to  reason.' 
When  we  regard  this  belief  in  connection  with  science, 
'  in  which  connection  it  receives  a  more  imposing  name, 
and  is  called  the  inductive  principle,'  the  result  is  the 
same.  '  The  inductive  principle  is  only  this  unreasoning 

impulse  applied  to  a  scientifically  ascertained  fact 

Science  has  led  up  to  the  fact ;  but  there  it  stops,  and  for 
converting  this  fact  into  a  law,  a  totally  unscientific  prin- 
ciple comes  into  play,  the  same  as  that  which  generalises 
the  commonest  observation  of  nature.' 

The  eloquent  pleader  of  the  cause  of  miracles  passes 
over  without  a  word  the  results  of  scientific  investigation, 
as  proving  anything  rational  regarding  the  principles  or 
method  by  which  such  results  have  been  achieved.  Here, 
as  elsewhere,  he  declines  the  test,  '  By  their  fruits  shall  ye 
know  them.'  Perhaps  our  best  way  of  proceeding  will 
be  to  give  one  or  two  examples  of  the  mode  in  which 
men  of  science  apply  the  unintelligent  impulse  with  which 
Mr.  Mozley  credits  them,  and  which  shall  show,  by  illustra- 
tion, the  surreptitious  method  whereby  they  climb  from 
the  region  of  facts  to  that  of  laws. 

Before  the  sixteenth  century  it  was  known  that  water 
rises  in  a  pump ;  the  effect  being  then  explained  by  the 
maxim  that  '  Nature  abhors  a  vacuum.'  It  was  not  known 
that  there  was  any  limit  to  the  height  to  which  the  water 
would  ascend,  until,  on  one  occasion,  the  gardeners  of 
Florence,  while  attempting  to  raise  water  to  a  very  great 
elevation,  found  that  the  column  ceased  at  a  height  of 
thirty-two  feet.  Beyond  this  all  the  skill  of  the  pump- 


:'/J4  FRAGMENTS   OF   SCIENCE. 

maker  could  not  get  it  to  rise.  The  fact  was  brought  to 
the  notice  of  Galileo,  and  he,  soured  by  a  world  which  had 
not  treated  his  science  over  kindly,  is  said  to  have  twitted 
the  philosophy  of  the  time  by  remarking  that  nature  evi- 
dently abhorred  a  vacuum  only  to  a  height  of  thirty-two 
feet.  Galileo,  however,  did  not  solve  the  problem.  It 
was  taken  up  by  his  pupil  Torricelli,  who  pondered  it, 
and,  in  doing  so,  various  thoughts  regarding  it  arose  in  his 
mind.  It  occurred  to  him  that  the  water  might  be  forced 
into  the  tube  by  a  pressure  applied  to  the  surface  of  the 
water  outside.  But  where,  under  the  actual  circumstances, 
was  such  a  pressure  to  be  found  ?  After  much  reflection, 
it  flashed  upon  Torricelli  that  the  atmosphere  might 
possibly  exert  this  pressure ;  that  the  impalpable  air 
might  possess  weight,  and  that  a  column  of  water  thirty- 
two  feet  high  might  be  of  the  exact  weight  necessary  to 
hold  the  pressure  of  the  atmosphere  in  equilibrium. 

There  is  much  in  this  process  of  pondering  and  its 
results,  which  it  is  impossible  to  analyse.  It  is  by  a  kind 
of  inspiration  that  we  rise  from  the  wise  and  sedulous 
contemplation  of  facts,  to  the  principles  on  which  they 
depend.  The  mind  is,  as  it  were,  a  photographic  plate, 
which  is  gradually  cleansed  by  the  effort  to  think  rightly, 
and  which,  when  so  cleansed,  and  not  before,  receives 
impressions  from  the  light  of  truth.  This  passage  from 
facts  to  principles  is  called  induction  ;  and  induction,  in 
its  highest  form,  is,  as  just  stated,  a  kind  of  inspiration. 
But,  to  make  it  sure,  the  inward  sight  must  be  shown 
to  be  in  accordance  with  outward  fact.  To  prove  or  dis- 
prove the  induction,  we  must  resort  to  deduction  and  ex- 
periment. 

Torricelli  reasoned  thus  :  If  a  column  of  water  thirty- 
two  feet  high  holds  the  pressure  of  the  atmosphere  in 
equilibrium,  a  shorter  column  of  a  heavier  liquid  ought 
to  do  the  same.  Now,  mercury  is  thirteen  times  heavier 


MIRACLES   AND    SPECIAL    PROVIDENCES.  395 

than  water ;  hence,  if  my  induction  be  correct,  the  at- 
mosphere ought  to  be  able  to  sustain  only  thirty  inches 
of  mercury.  Here,  then,  is  a  deduction  which  can  be 
immediately  submitted  to  experiment.  Torricelli  took  a 
glass  tube  a  yard  or  so  in  length,  closed  at  one  end  and 
open  at  the  other,  and  filling  it  with  mercury,  he  stopped 
the  open  end  with  his  thumb,  and  inverted  it  in  a  basin 
filled  with  the  liquid  metal.  One  can  imagine  the  feel- 
ing with  which  Torricelli  removed  his  thumb,  and  the 
delight  he  experienced  when  he  found  that  his  thought 
had  forestalled  a  fact  never  before  revealed  to  human 
eyes.  The  column  sank,  but  it  ceased  to  sink  at  a  height 
of  thirty  inches,  leaving  the  Torricellian  vacuum  over- 
head. From  that  hour  the  theory  of  the  pump  was  es- 
tablished. 

The  celebrated  Pascal  followed  Torricelli  with  another 
deduction.  He  reasoned  thus  :  If  the  mercurial  column 
be  supported  by  the  atmosphere,  the  higher  we  ascend  in 
the  air,  the  lower  the  column  ought  to  sink,  for  the  less 
will  be  the  weight  of  the  air  overhead.  He  caused  a 
friend  to  ascend  the  Puy  de  Dome,  carrying  with  him  a 
barometric  column;  and  it  was  found  that  during  the 
ascent  the  column  sank,  and  that  during  the  subsequent 
descent  the  column  rose. 

Between  the  time  here  referred  to  and  the  present, 
millions  of  experiments  have  been  made  upon  this  subject. 
Every  village  pump  is  an  apparatus  for  such  experiments. 
In  thousands  of  instances,  moreover,  pumps  have  refused 
to  work  ;  but  on  examination  it  has  infallibly  been  found 
that  the  well  was  dry,  that  the  pump  required  priming, 
or  that  some  other  defect  in  the  apparatus  accounted  for 
the  anomalous  action.  In  every  case  of  the  kind  the  skill 
of  the  pump-maker  has  been  found  to  be  the  true  remedy. 
In  no  case  has  the  pressure  of  the  atmosphere  ceased  ; 
constancy,  as  regards  the  lifting  of  pump-water,  has  been 


396  FRAGMENTS   OF   SCIENCE. 

hitherto  the  demonstrated  rule  of  nature.  So  also  as 
regards  Pascal's  experiment.  His  experience  has  been 
the  universal  experience  ever  since.  Men  have  climbed 
mountains,  and  gone  up  in  balloons;  but  no  deviation 
from  Pascal's  result  has  ever  been  observed.  Barometers, 
like  pumps,  have  refused  to  act ;  but  instead  of  indicating 
any  suspension  of  the  operations  of  nature,  or  any  inter- 
ference on  the  part  of  its  Author  with  atmospheric  pres- 
sure, examination  has  in  every  instance  fixed  the  anomaly 
upon  the  instruments  themselves.  It  is  this  welding, 
then,  of  rigid  logic  to  verifying  fact  that  Mr.  Mozley 
refers  to  an  '  unreasoning  impulse.' 

Let  us  now  briefly  consider  the  case  of  Newton.  Be- 
fore his  time  men  had  occupied  themselves  with  the  pro- 
blem of  the  solar  system.  Kepler  had  deduced,  from  a 
vast  mass  of  observations,  those  general  expressions  of 
planetary  motion  known  as  '  Kepler's  laws.'  It  had  been 
observed  that  a  magnet  attracts  iron;  and  by  one  of 
those  flashes  of  inspiration,  which  reveal  to  the  human 
mind  the  vast  in  the  minute,  the  general  in  the  particular, 
it  had  been  inferred,  that  the  force  by  which  bodies  fall 
to  the  earth  might  also  be  an  attraction.  Newton  pon- 
dered all  these  things.  He  had  a  great  power  of  ponder- 
ing. He  coidd  look  into  the  darkest  subject  until  it 
became  entirely  luminous.  How  this  light  arises  we  can- 
not explain ;  but,  as  a  matter  of  fact,  it  does  arise.  Let 
me  remark  'here,  that  this  power  of  pondering  facts  is 
one  with  which  the  ancients  could  have  been  but  imper- 
fectly acquainted.  They,  for  the  most  part,  found  the 
exercise  of  fantasy  more  pleasant  than  the  brooding  over 
facts.  Hence  it  is,  that  when  those  whose  education  has 
been  derived  from  the  ancients  speak  of  'the  reason  of 
man,'  they  are  apt  to  omit  from  their  conception  of  reason 
one  of  its  greatest  powers.  Well,  Newton  slowly  mar- 
shalled his  thoughts,  or  rather  they  came  to  him  while  he 


MIRACLES  AND    SPECIAL   PROVIDENCES.  297 

intended  his  mind,'  rising  like  a  series  of  intellectual 
births  out  of  chaos.  He  made  this  idea  of  attraction  his 
own.  But,  to  apply  the  idea  to  the  solar  system,  it  was 
necessary  to  know  the  magnitude  of  the  attraction,  and 
the  law  of  its  variation  with  the  distance.  His  concep- 
tions first  of  all  passed  from  the  action  of  the  earth  as  a 
whole,  to  that  of  its  constituent  particles.  And  persistent 
thought  brought  more  and  more  clearly  out  the  final 
divination,  that  every  particle  of  matter  attracts  every 
other  particle  with  a  force  varying  inversely  as  the  square 
of  the  distance  between  the  particles. 

This  is  Newton's  celebrated  law  of  inverse  squares. 
Here  we  have  the  flower  and  outcome  of  his  induction; 
and  how  to  verify  it,  or  to  disprove  it,  was  the  next  ques- 
tion. The  first  step  of  Newton  in  this  direction  was  to 
prove,  mathematically,  that  if  this  law  of  attraction  be 
the  true  one ;  if  the  earth  be  constituted  of  particles 
which  obey  this  law ;  then  the  action  of  a  sphere  equal 
to  the  earth  in  size  on  a  body  outside  of  it,  is  the  same 
as  that  which  would  be  exerted  if  the  whole  mass  of  the 
sphere  were  contracted  to  a  point  at  its  centre.  Practi- 
cally speaking,  then,  the  centre  of  the  earth  is  the  point 
from  which  distances  must  be  measured  to  bodies  attracted 
by  the  earth. 

From  experiments  executed  before  his  time,  Newton 
knew  the  amount  of  the  earth's  attraction  at  the  earth's 
surface,  or  at  a  distance  of  4,000  miles  from  its  centre. 
His  object  now  was  to  measure  the  attraction  at  a  greater 
distance,  and  thus  to  determine  the  law  of  its  diminu- 
tion. But  how  was  he  to  find  a  body  at  a  sufficient 
distance  ?  He  had  no  balloon ;  and  even  if  he  had,  he 
knew  that  any  height  to  which  he  could  attain  would  be 
too  small  to  enable  him  to  solve  his  problem.  What  did 
he  do  ?  He  fixed  his  thoughts  upon  the  moon  ; — a  body 
240,000  miles,  or  sixty  times  the  earth's  radius,  from  the 


308  FKAOMKXTS   OF   SCIENCE. 

earth's  centre.  He  virtually  weighed  the  moon,  and 
found  that  weight  to  be  -y^-Vo^  of  what  it  would  be  at 
the  earth's  surface.  This  is  exactly  what  his  theory  re- 
quired. I  will  not  dwell  here  upon  the  pause  of  .Newton 
after  his  first  calculations,  or  speak  of  his  self-denial  in 
withholding  them,  because  they  did  not  quite  agree  with 
the  observations  then  at  his  command.  Newton's  action 
in  this  matter  is  the  normal  action  of  the  scientific  mind, 
If  it  were  otherwise — if  scientific  men  were  not  accus- 
tomed to  demand  verification — if  they  were  satisfied 
with  the  imperfect  while  the  perfect  is  attainable,  their 
science,  instead  of  being,  as  it  is,  a  fortress  of  adamant, 
would  be  a  house  of  clay,  ill-fitted  to  bear  the  buffetings 
of  the  theologic  storms  to  which  it  is  periodically 
exposed. 

Thus  we  see  that  Newton,  like  Torricelli,  first  pon- 
dered his  facts,  illuminated  them  with  persistent  thought, 
and  finally  divined  the  character  of  the  force  of  gravita- 
tion. But,  having  thus  travelled  inward  to  the  principle, 
he  reversed  his  steps,  carried  the  principle  outwards, 
and  justified  it  by  demonstrating  its  fitness  to  external 
nature. 

And  here,  in  passing,  I  would  notice  a  point  which  is 
well  worthy  of  attention.  Kepler  had  deduced  his  laws 
from  observation.  As  far  back  as  those  observations 
extended,  the  planetary  motions  had  obeyed  these  laws  ; 
and  neither  Kepler  nor  Newton  entertained  a  doubt  as 
to  their  continuing  to  obey  them.  Year  after  year,  as 
the  ages  rolled,  they  believed  that  those  laws  would  con- 
tinue to  illustrate  themselves  in  the  heavens.  But  this 
was  not  sufficient.  The  scientific  mind  can  find  no  re- 
pose in  the  mere  registration  of  sequence  in  nature. 
The  further  question  intrudes  itself  with  resistless  might, 
Whence  comes  the  sequence?  What  is  it  that  binds 
the  consequent  to  its  antecedent  in  nature  ?  The  truly 


MIRACLES   AND    SPECIAL    PROVIDENCES.  399 

scientific  intellect  never  can  attain  rest  until  it  reaches 
the  forces  by  which  the  observed  succession  is  produced. 
It  was  thus  with  Torricelli ;  it  was  thus  with  Newton ; 
it  is  thus  pre-eminently  with  the  scientific  man  of  to- 
day. In  common  with  the  most  ignorant,  he  shares 
the  belief  that  spring  will  succeed  winter,  that  summer 
will  succeed  spring,  that  autumn  will  succeed  summer,  and 
that  winter  will  succeed  autumn.  But  he  knows  still 
further — and  this  knowledge  is  essential  to  his  intellectual 
repose — that  this  succession,  besides  being  permanent, 
is,  under  the  circumstances,  newssary;  that  the  gravi- 
tating force  exerted  between  the  sun,  and  a  revolving 
sphere  with  an  axis  inclined  to  the  plane  of  its  orbit, 
must  produce  the  observed  succession  of  the  seasons. 
Not  until  this  relation  between  forces  and  phenomena 
has  been  established,  is  the  law  of  reason  rendered 
concentric  with  the  law  of  nature ;  and  not  until  this  is 
effected  does  the  mind  of  the  scientific  philosopher  rest 
in  peace. 

The  expectation  of  likeness,  then,  in  the  procession  of 
phenomena,  is  not  that  on  which  the  scientific  mind 
founds  its  belief  in  the  order  of  nature.  If  the  force  be 
permanent  the  phenomena  are  necessary,  whether  they 
resemble  or  do  not  resemble  anything  that  has  gone 
before.  Hence,  in  judging  of  the  order  of  nature,  our 
enquiries  eventually  relate  to  the  permanence  of  force. 
From  Galileo  to  Newton,  from  Newton  to  our  own  time, 
eager  eyes  have  been  scanning  the  heavens,  and  clear 
heads  have  been  pondering  the  phenomena  of  the  solar 
system.  The  same  eyes  and  minds  have  been  also  ob- 
serving, experimenting,  and  reflecting  on  the  action  of 
gravity  at  the  surface  of  the  earth.  Nothing  has  occurred 
to  indicate  that  the  operation  of  the  law  has  for  a  mo- 
ment been  suspended ;  nothing  has  ever  intimated  that 
nature  has  been  crossed  by  spontaneous  action,  or  that  a 


400  FRAGMENTS   OP   SCIENCE. 

state  of  things  at  any  time  existed  which  could  not  be 
rigorously  deduced  from  the  preceding  state. 

Given  the  distribution  of  matter,  and  the  forces  in 
operation,  in  the  time  of  Galileo,  the  competent  mathe- 
matician of  that  day  could  predict  what  is  now  occurring 
in  our  own.  We  calculate  eclipses  in  advance,  and  find 
our  calculations  true  to  the  second.  We  determine  the 
dates  of  those  that  have  occurred  in  the  early  times  of 
history,  and  find  calculation  and  history  at  peace.  Ano- 
malies and  perturbations  in  the  planets  have  been  over 
and  over  again  observed;  but  these,  instead  of  demon- 
strating any  inconstancy  on  the  part  of  natural  law,  have 
invariably  been  reduced  to  consequences  of  that  law.  In- 
stead of  referring  the  perturbations  of  Uranus  to  any 
interference  on  the  part  of  the  Author  of  nature  with  the 
law  of  gravitation,  the  question  which  the  astronomer  pro- 
posed to  himself  was,  '  How,  in  accordance  with  this  law, 
can  the  perturbation  be  produced  ?  '  Guided  by  a  principle, 
he  was  enabled  to  fix  the  point  of  space  in  which,  if  a 
mass  of  matter  were  placed,  the  observed  perturbations 
would  follow.  We  know  the  result.  The  practical  as- 
tronomer turned  his  telescope  towards  the  region  which 
the  intellect  of  the  theoretic  astronomer  had  already  ex- 
plored, and  the  planet  now  named  Neptune  was  found  in 
its  predicted  place.  A  very  respectable  outcome,  it  will 
be  admitted,  of  an  impulse  which  '  rests  upon  no  rational 
grounds,  and  can  be  traced  to  no  rational  principle ; ' 
which  possesses  '  no  intellectual  character ; '  which  '  philo- 
sophy '  has  uprooted  from  *  the  ground  of  reason,'  and 
fixed  in  that '  large  irrational  department '  discovered  for 
it,  by  Mr.  Mozley,  in  the  hitherto  unexplored  wilderness 
of  the  human  mind. 

The  proper  function  of  the  inductive  principle,  or  the 
belief  in  the  order  of  nature,  says  Mr.  Mozley,  is  '  to  act 
as  a  practical  basis  for  the  affairs  of  life,  and  the  carrying 


MIRACLES  AND   SPECIAL  PROVIDENCES.  40] 

on  of  human  society.'  But  what,  it  may  be  asked,  has 
the  planet  Neptune,  or  the  belts  of  Jupiter,  or  the  white- 
ness about  the  poles  of  Mars,  to  do  with  the  affairs  of 
society?  How  is  society  affected  by  the  fact  that  the 
sun's  atmosphere  contains  sodium,  or  that  the  nebula  of 
Orion  contains  hydrogen  gas  ?  Nineteen- twentieths  of 
the  force  employed  in  the  exercise  of  the  inductive  prin- 
ciple, which,  reiterates  Mr.  Mozley,  is  '  purely  practical,' 
have  been  expended  upon  subjects  as  unpractical  as  these. 
What  practical  interest  has  society  in  the  fact  that  the 
spots  on  the  sun  have  a  decennial  period,  and  that  when 
a  magnet  is  closely  watched  for  half  a  century,  it  is  found 
to  perform  small  motions  which  synchronise  with  the 
appearance  and  disappearance  of  the  solar  spots?  And 
yet,  I  doubt  not,  Sir  Edward  Sabine  would  deem  a  life  of 
intellectual  toil  amply  rewarded  by  being  privileged  to 
solve,  at  its  close,  these  infinitesimal  motions. 

The  inductive  principle  is  founded  in  man's  desire  to 
know — a  desire  arising  from  his  position  among  phenomena 
which  are  reducible  to  order  by  his  intellect.  The  material 
universe  is  the  complement  of  the  intellect ;  and,  without 
the  study  of  its  laws,  reason  could  never  have  awakened  to 
the  higher  forms  of  self-consciousness  at  all.  It  is  the 
non-ego,  through  and  by  which  the  ego  is  endowed  with 
self-discernment.  We  hold  it  to  be  an  exercise  of  reason 
to  explore  the  meaning  of  a  universe  to  which  we  stand 
in  this  relation,  and  the  work  we  have  accomplished  is 
the  proper  commentary  on  the  methods  we  have  pursued. 
Before  these  methods  were  adopted  the  unbridled  imagina- 
tion roamed  through  nature,  putting  in  the  place  of  law 
the  figments  of  superstitious  dread.  For  thousands  of 
years  witchcraft,  and  magic,  and  miracles,  and  special 
providences,  and  Mr.  Mozley's  '  distinctive  reason  of  man,' 
had  the  world  to  themselves.  They  made  worse  than 
nothing  of  it — worse,  I  say,  because  they  let  and  hindered 


402  FRAGMENTS    OP   SCIENCE. 

those  who  might  have  made  something  of  it.  Hence  it 
is,  that  during  a  single  lifetime  of  this  era  of  '  unintelligent 
impulse,'  the  progress  in  knowledge  is  all  but  infinite  as 
compared  with  that  of  the  ages  which  preceded  ours. 

The  believers  in  magic  and  miracles  of  a  couple  of 
centuries  ago  had  all  the  strength  of  Mr.  Mozley's  present 
logic  on  their  side.  They  had  done  for  themselves  what 
lie  rejoices  in  having  so  effectually  done  for  us — cleared 
the  ground  of  the  belief  in  the  order  of  nature,  and  declared 
magic,  miracles,  and  witchcraft  to  be  matters  for  '  ordinary 
evidence '  to  decide.  '  The  principle  of  miracles '  thus 
'befriended'  had  free  scope,  and  we  know  the  result. 
Lacking  that  rock-barrier  of  natural  knowledge  which  we, 
laymen  of  England,  now  possess,  keen  jurists  and  cultivated 
men  were  hurried  on  to  deeds,  the  bare  recital  of  which 
makes  the  blood  run  cold.  Skilled  in  all  the  rules  of 
human  evidence,  and  versed  in  all  the  arts  of  cross-ex- 
amination, these  men,  nevertheless,  went  systematically 
astray,  and  committed  the  deadliest  wrongs  against 
humanity.  And  why?  Because  they  could  not  put  Nature 
into  the  witness-box,  and  question  her ;  of  her  voiceless 
1  testimony '  they  knew  nothing.  In  all  cases  between 
man  and  man,  their  judgment  was  to  be  relied  on ;  but 
in  all  cases  between  man  and  nature,  they  were  blind 
leaders  of  the  blind.1 

Mr.  Mozley  concedes  that  it  would  be  no  great  result 
if  miracles  were  only  accepted  by  the  ignorant  and  super- 
stitious, '  because  it  is  easy  to  satisfy  those  who  do  not 

1  'In  166i  two  women  were  hung  in  Suffolk,  under  a  sentence  of  Sir 
Matthew  Hale,  who  took  the  opportunity  of  declaring  that  the  re.-tlity  of 
witchcraft  was  unquestionable ;  "  for  first,  the  Scriptures  had  affirmed  so 
much  ;  and  secondly,  the  wisdom  of  all  nations  had  provided  laws  against 
such  persons,  which  is  an  argument  of  their  confidence  of  such  a  crime." 
Sir  Thomas  Browne,  who  was  a  great  physician  as  well  as  a  great  writer, 
•was  railed  as  a  witness,  and  swore  "that  he  was  clearly  of  opinion  that  the 
persons  were  bewitched."'— Lecky's  History  of  Rationalism,  vol.  i.  p.  120. 


MIRACLES   AND    SPECIAL   PROVIDENCES.  403 

enquire.'  But  he  does  consider  it  '  a  great  result '  that 
they  have  been  accepted  by  the  educated.  In  what  sense 
educated  ?  Like  those  statesmen,  jurists,  and  church 
dignitaries  whose  education  was  unable  to  save  them  from 
the  frightful  errors  glanced  at  above  ?  Not  even  in  this 
sense ;  for  the  great  mass  of  Mr.  Mozley's  educated  people 
had  no  legal  training,  and  must  have  been  absolutely 
defenceless  against  delusions  which  could  set  even  that 
training  at  naught.  Like  nine-tenths  of  our  clergy  at  the 
present  day,  they  were  versed  in  the  literature  of  Greece, 
Kome,  and  Judea ;  but  as  regards  a  knowledge  of  nature, 
which  is  here  the  one  thing  needful,  they  were  '  noble 
savages,'  and  nothing  more.  In  the  case  of  miracles,  then, 
it  behoves  us  to  understand  the  weight  of  the  negative, 
before  we  assign  a  value  to  the  positive ;  to  comprehend 
the  depositions  of  nature  before  we  attempt  to  measure, 
with  them,  the  evidence  of  men.  "We  have  only  to  open 
our  eyes  to  see  what  honest  and  even  intellectual  men 
and  women  arc  capable  of,  as  to  judging  evidence,  in  this 
nineteenth  century  of  the  Christian  era,  and  in  latitude 
fifty-two  degrees  north.  The  experience  thus  gained 
ought,  I  imagine,  to  influence  our  opinion  regarding  the 
testimony  of  people  inhabiting  a  sunnier  clime,  with  a 
richer  imagination,  and  without  a  particle  of  that  restraint 
which  the  discoveries  of  physical  science  have  imposed 
upon  mankind. 

Having  thus  submitted  Mr.  Mozley's  views  to  the  ex- 
amination which  they  challenged  at  the  hands  of  a  student 
of  nature,  I  am  unwilling  to  quit  his  book  without  ex- 
pressing my  high  admiration  and  respect  for  his  ability. 
His  failure,  as  I  consider  it  to  be,  must,  I  think,  await  all 
attempts,  however  able,  to  deal  with  the  material  unwei.se 
by  logic  and  imagination,  unaided  by  experiment  ?nd 
observation.  With  regard  to  the  style  of  the  book,  I 


t04  FRAGMENTS   OF   SCIENCE. 

willingly  subscribe  to  the  description  with  which  the 
1  Times  '  winds  up  its  able  and  appreciative  review.  '  It 
is  marked  throughout  with  the  most  serious  and  earnest 
conviction,  but  is  without  a  single  word  from  first  to  last 
of  asperity  or  insinuation  against  opponents,  and  this  not 
from  any  deficiency  of  feeling  as  to  the  importance  of  the 
issue,  but  from  a  deliberate  and  resolutely  maintained 
self-control,  and  from  an  over-ruling,  ever-present  sense 
of  the  duty,  on  themes  like  these,  of  a  more  than  judicial 
calmness.' 

[To  the  argument  regarding  the  quantity  of  the  mira- 
culous, introduced  at  page  387,  Mr.  Mozley  has  done  me 
the  honour  of  publishing  a  Reply  in  the  seventh  volume 
of  the  '  Contemporary  Review.' — J.  T.] 


ADDITIONAL  REMARKS  ON  MIRACLES. 

AMONG  the  scraps  of  manuscript,  written  at  the  time 
when  Mr.  Mozley's  work  occupied  my  attention,  I  find  the 
following  reflections : — 

With  regard  to  the  influence  of  modern  science  which 
Mr.  Mozley  rates  so  low,  one  obvious  effect  of  it  is  to 
enhance  the  magnitude  of  many  of  the  recorded  miracles, 
and  to  increase  proportionably  the  difficulties  of  belief. 
The  ancients  knew  but  little  of  the  vastness  of  the  universe. 
The  Rev.  Mr.  Kirkman,  for  example,  has  shown  what  in 
adequate  notions  the  Jews  entertained  regarding  the 
4  firmament  of  heaven  ; '  and  Professor  Airy  refers  to  the 
case  of  a  Greek  philosopher  who  was  persecuted  for 
hazarding  the  assertion,  then  deemed  monstrous,  that  the 
sun  might  be  as  large  as  the  whole  country  of  Greece. 
The  concerns  of  a  universe,  regarded  from  this  point  of 


REMAKES   ON   MIKACLES.  405 

view,  were  much  more  commensurate  with  man  and  his 
concerns  than  those  of  the  universe  which  science  now 
reveals  to  us ;  and  hence  that  to  suit  man's  purposes,  or 
that  in  compliance  with  his  prayers,  changes  should  occur 
in  the  order  of  the  universe,  was  more  easy  of  belief  in 
the  ancient  world  than  it  can  be  now.  In  the  very  magni- 
tude which  it  assigns  to  natural  phenomena,  science  has 
augmented  the  distance  between  them  and  man,  and  in- 
creased the  popular  belief  in  their  orderly  progression. 

As  a  natural  consequence  the  demand  for  evidence  is 
more  exacting  than  it  used  to  be,  whenever  it  is  affirmed 
that  the  order  of  nature  has  been  disturbed.  Let  us  take 
as  an  illustration  the  miracle  by  which  the  victory  of  Joshua 
over  the  Amorites  was  rendered  complete.  In  this  case 
the  sun  is  reported  to  have  stood  still  for  4  a  whole  day ' 
upon  Gribeon,  and  the  moon  in  the  valley  of  Ajalon.  An 
Englishman  of  average  education  at  the  present  day  would 
naturally  demand  a  greater  amount  of  evidence  to  prove 
that  this  occurrence  took  place,  than  would  have  satisfied 
an  Israelite  in  the  age  succeeding  that  of  Joshua.  For, 
to  the  one,  the  miracle  probably  consisted  of  the  stoppage 
of  a  fiery  ball  less  than  a  yard  in  diameter,  while  to  the 
other  it  would  be  the  stoppage  of  an  orb  fourteen  hundred 
thousand  times  the  earth  in  size.  And  even  accepting 
the  interpretation  that  Joshua  dealt  with  what  was  apparent 
merely,  but  that  what  really  occurred  was  the  suspension  of 
the  earth's  rotation,  I  think  the  right  to  exercise  a  greater 
reserve  in  accepting  the  miracle,  and  to  demand  stronger 
evidence  in  support  of  it  than  that  which  would  have 
satisfied  an  ancient  Israelite,  or  than  that  which  would 
now  satisfy  the  archaic  editor  of  the  '  Dublin  Review,'  will 
still  be  conceded  to  a  man  of  science. 

There  is  a  scientific  as  well  as  a  historic  imagination  ; 
and  when,  by  the  exercise  of  the  former,  the  stoppage  of 
the  earth's  rotation  is  clearly  realised,  the  event  assumes 


106  FRAGMENTS    OF   SCIENCE. 

proportions  so  vast,  in  comparison  with  the  result  to  be 
obtained  by  it,  that  belief  reels  under  the  reflection.  The 
energy  here  involved  is  equal  to  that  of  six  trillions  of 
horses  working  for  the  whole  of  the  time  employed  by 
Joshua  in  the  destruction  of  his  foes.  The  amount  of 
power  thus  expended  would  be  sufficient  to  supply  every 
individual  of  an  army  a  thousand  times  the  strength  of 
that  of  Joshua,  with  a  thousand  times  the  fighting  power 
of  each  of  Joshua's  soldiers,  not  for  the  few  hours  necessary 
to  the  extinction  of  a  handful  of  Amorites,  but  for  millions 
of  years.  All  this  wonder  is  silently  passed  over  by  the 
sacred  historian,  confessedly  because  he  knew  nothing 
about  it.  Whether,  therefore,  we  consider  the  miracle  as 
purely  evidential,  or  as  a  practical  means  of  vengeance, 
the  same  lavish  squandering  of  energy  stares  us  in  the 
face.  If  evidential,  the  energy  was  wasted,  because  the 
Israelites  knew  nothing  of  its  amount;  if  simply  de- 
structive, thei  the  ratio  of  the  quantity  lost  to  that 
employed,  may  be  inferred  from  the  foregoing  figures. 

To  other  miracles  similar  remarks  apply.  Transferring 
our  thoughts  from  this  little  sand-grain  of  an  earth  to  the 
immeasurable  heavens,  where  countless  worlds  with  freights 
of  life  probably  revolve  unseen,  the  very  suns  which  warm 
them  being  barely  visible  across  abysmal  space ;  reflecting 
that  beyond  these  sparks  of  solar  fire,  suns  innumerable 
may  burn,  whose  light  can  never  stir  the  optic  nerve  at  all ; 
and  bringing  these  reflections  face  to  face  with  the  idea  of 
the  Builder  and  Sustainer  of  it  all  showing  Himself  in  a 
burning  bush,  exhibiting  His  hinder  parts,  or  behaving 
in  other  familiar  ways  ascribed  to  Him  in  the  Jew- 
ish Scriptures,  the  incongruity  must  appear.  Did  this 
credulous  prattle  of  the  ancients  about  miracles  stand 
alone ;  were  it  not  associated  with  words  of  imperish- 
able wisdom,  and  with  examples  of  moral  grandeur  un- 
matched elsewhere  in  the  history  of  the  human  race, 


REMARKS    ON  MIRACLES.  407 

both  the  miracles  and  their  «  evidences '  would  have  long 
since  ceased  to  be  the  transmitted  inheritance  of  intelligent 
men.  Influenced  by  the  thoughts  which  this  universe 
inspires,  well  may  we  exclaim  in  David's  spirit,  if  not  in 
David's  words  :  '  When  I  consider  the  heavens,  the  work 
of  thy  fingers,  the  moon,  and  the  stars,  which  thou  has! 
ordained ;  what  is  man  that  thou  shouldst  be  mindful  ol 
him,  or  the  son  of  man  that  thou  shouldst  so  regard  him  ?  '' 
If  you  ask  me  who  is  to  limit  the  outgoings  of  Almighty 
power,  my  answer  is,  not  I.  If  you  should  urge  that  if 
the  Builder  and  the  Maker  of  this  universe  chose  to  stop 
the  rotation  of  the  earth,  or  to  take  the  form  of  a  burning 
bush,  there  is  nothing  to  prevent  Him  from  doing  so,  I  am 
not  prepared  to  contradict  you.  I  neither  agree  with  you 
nor  differ  from  -you,  for  it  is  a  subject  of  which  I  know 
nothing.  But  I  observe  that  in  such  questions  regarding 
Almighty  power,  your  enquiries  relate,  not  to  that  power 
as  it  is  actually  displayed  in  the  universe,  but  to  the 
power  of  your  own  imagination.  Your  question  is,  not 
has  the  Omnipotent  done  so  and  so  ?  or  is  it  in  the 
least  degree  likely  that  the  Omnipotent  should  do  so 
and  so  ?  but,  is  my  imagination  competent  to  picture  a 
Being  able  and  willing  to  do  so  and  so  ?  I  am  not  pre- 
pared to  deny  your  competence.  To  the  human  mind 
belongs  the  faculty  of  enlarging  and  diminishing,  of  dis- 
torting and  combining,  indefinitely  the  objects  revealed 
by  the  senses.  It  can  imagine  a  mouse  as  large  as 
an  elephant,  an  elephant  as  large  as  a  mountain,  and  a 
mountain  as  high  as  the  stars.  It  can  separate  congruities 
and  unite  incongruities.  "We  see  a  fish  and  we  see  a 
woman  ;  we  can  drop  one  half  of  each,  and  unite  in  idea 
the  other  two  halves  to  a  mermaid.  We  see  a  horse  and 
we  see  a  man  ;  we  are  able  to  drop  one  half  of  each,  and 
unite  the  other  two  halves  to  a  centaur.  Thus  also  the 
pictorial  representations  of  the  Deity,  the  bodies  and  wings 


108  FRAGMENTS    OF   SCIENCE. 

of  cherubs  and  seraphs,  the  hoofs,  horns,  and  tail  of  the 
Evil  One,  the  joys  of  the  blessed,  and  the  torments  of  the 
damned,  have  been  elaborated  from  materials  furnished  to 
the  imagination  by  the  senses.  And  it  behoves  you  and 
me  to  take  care  that  our  notions  of  the  Power  which  rules 
the  universe  are  not  mere  fanciful  or  ignorant  enlarge- 
ments of  human  power.  The  capabilities  of  what  you  call 
your  reason  are  not  denied.  By  the  exercise  of  the  faculty 
here  adverted  to,  you  can  picture  to  yourself  a  Being  able 
and  willing  to  do  any  and  every  conceivable  thing.  You 
are  right  in  saying  that  in  opposition  to  this  Power  science 
is  of  no  avail.  Mr.  Mozley  would  call  it  *  a  weapon  of 
air.'  The  man  of  science,  however,  while  accepting  the 
figure,  would  probably  reverse  its  application,  thinking  it  is 
not  science  which  is  here  the  thing  of  air,  but  that  unsub- 
stantial pageant  of  the  imagination  to  which  the  solidity 
of  science  is  opposed. 


III. 

SCIENTIFIC  MATERIALISM. 


rPHE  celebrated  Fichte,  in  his  lectures  on  the  *  Voca- 
-L  tion  of  the  Scholar,'  insisted  on  a  culture  which  should 
not  be  one-sided,  but  all-sided.  The  scholar's  intellect  was 
to  expand  spherically,  and  not  in  a  single  direction  only.  In 
one  direction,  however,  Fichte  required  that  the  scholar 
should  apply  himself  directly  to  nature,  become  a  creator 
of  knowledge,  and  thus  repay,  by  original  labours  of  his 
own,  the  immense  debt  he  owed  to  the  labours  of  others. 
It  was  these  which  enabled  him  to  supplement  the  know- 
ledge derived  from  his  own  researches,  so  as  to  render  his 
culture  rounded  and  not  one-sided. 

As  regards  science,  Fichte's  idea  is  to  some  extent 
illustrated  by  the  constitution  and  labours  of  the  British 
Association.  We  have  here  a  body  of  men  engaged 
in  the  pursuit  of  Natural  Knowledge,  but  variously 
engaged.  While  sympathising  with  each  of  its  depart- 
ments, and  supplementing  his  culture  by  knowledge 
drawn  from  all  of  them,  each  student  amongst  us  selects 
one  subject  for  the  exercise  of  his  own  original  faculty — 
one  line,  along  which  he  may  carry  the  light  of  his  private 
intelligence  a  little  way  into  the  darkness  by  which  all 
knowledge  is  surrounded.  Thus,  the  geologist  deals  with 
the  rocks ;  the  biologist  with  the  conditions  and  pheno- 
mena of  life ;  the  astronomer  with  stellar  masses  and 
motions:  the  mathematician  with  the  relations  of 


410  FEAGMEJsTS   OF   SCIENCE. 

space  and  number  ;  the  chemist  pursues  his  atoms  ;  while 
the  physical  investigator  has  his  own  large  field  in  optical, 
thermal,  electrical,  acoustical,  and  other  phenomena. 
The  British  Association  then,  as,  a  whole,  faces  physical 
nature  on  all  sides,  and  pushes  knowledge  centrifugally 
outwards,  the  sum  of  its  labours  constituting  what  Fichte 
might  call  the  sphere  of  natural  knowledge.  In  the 
meetings  of  the  Association  it  is  found  necessary  to  re- 
solve this  sphere  into  its  component  parts,  which  take 
concrete  form  under  the  respective  letters  of  our  Sections. 

This  is  the  Mathematical  and  Physical  Section. 
Mathematics  and  physics  have  been  long  accustomed  to 
coalesce.  For,  no  matter  how  subtle  a  natural  pheno- 
menon may  be,  whether  we  observe  it  in  the  region  of 
sense,  or  follow  it  into  that  of  imagination,  it  is  in  the 
long  run  reducible  to  mechanical  laws.  But  the  me- 
chanical data  once  guessed  or  given,  mathematics  become 
all-powerful  as  an  instrument  of  deduction.  The  com- 
mand of  Geometry  over  the  relations  of  space,  and  the  far- 
reaching  power  which  Analysis  confers,  are  potent  both  as 
means  of  physical  discovery,  and  of  reaping  the  entire 
fruits  of  discovery.  Indeed,  without  mathematics,  ex- 
pressed or  implied,  our  knowledge  of  physical  science 
would  be  both  friable  and  incomplete. 

Side  by  side  with  the  mathematical  method  we  have 
the  method  of  experiment.  Here,  from  a  starting-point 
furnished  by  his  own  researches  or  those  of  others,  the 
investigator  proceeds  by  combining  intuition  and  veri- 
fication. He  ponders  the  knowledge  he  possesses,  and 
tries  to  push  it  further;  he  guesses, and  checks  his  guess ; 
he  conjectures,  and  confirms  or  explodes  his  conjecture. 
These  guesses  and  conjectures  are  by  no  means  leaps  in 
the  dark ;  for  knowledge  once  gained  casts  a  faint 
light  beyond  its  own  immediate  boundaries.  There  is  no 
discovery  so  limited  as  not  to  illuminate  something 


SCIENTIFIC   MATERIALISM.  411 

beyond  itself.  The  force  of  intellectual  penetration  into 
this  penurnbral  region  which  surrounds  actual  knowledge 
is  not,  as  some  seem  to  think,  dependent  upon  method, 
but  upon  the  genius  of  the  investigator.  There  is,  how- 
ever, no  genius  so  gifted  as  not  to  need  control  and  veri- 
fication. The  profoundest  minds  know  best  that  Nature's 
ways  are  not  at  all  times  their  ways,  and  that  the  bright- 
est flashes  in  the  world  of  thought  are  incomplete  until 
they  have  been  proved  to  have  their  counterparts  in  the 
world  of  fact.  Thus  the  vocation  of  the  true  experiment- 
alist may  be  defined  as  the  continued  exercise  of  spiritual 
insight,  and  its  incessant  correction  and  realisation.  His 
experiments  constitute  a  body,  of  which  his  purified  in- 
tuitions are,  as  it  were,  the  soul. 

Partly  through  mathematical  and  partly  through  ex- 
perimental research,  physical  science  has,  of  late  years,  as- 
sumed a  momentous  position  in  the  world.  Both  in  a 
material  and  in  an  intellectual  point  of  view  it  has 
produced,  and  it  is  destined  to  produce,  immense  changes 
— vast  social  ameliorations,  and  vast  alterations  in  the 
popular  conception  of  the  origin,  rule,  and  governance  of 
natural  things.  By  science,  in  the  physical  world,  mira- 
cles are  wrought,  while  philosophy  is  forsaking  its  ancient 
metaphysical  channels,  and  pursuing  others  which  have 
been  opened,  or  indicated,  by  scientific  research.  This 
must  become  more  and  more  the  case  as  philosophical 
writers  become  more  deeply  imbued  with  the  methods  of 
science,  better  acquainted  with  the  facts  which  scientific 
men  have  established,  and  with  the  great  theories  which 
they  have  elaborated. 

If  you  look  at  the  face  of  a  watch,  you  see  the  hour 
and  minute-hands,  and  possibly  also  a  second-hand, 
moving  over  the  graduated  dial.  Why  do  these  hands 
move  ?  and  why  are  their  relative  motions  such  as  they 
are  observed  to  be  ?  These  questions  cannot  be  answered 
20 


412  FRAGMENTS    OF   SCIENCE. 

without  opening  the  watch,  mastering  its  various  parts, 
and  ascertaining  their  relationship  to  each  other.  When 
this  is  done,  we  land  that  the  observed  motion  of  the 
hands  follows  of  necessity  from  the  inner  mechanism  of 
the  watch,  when  acted  upon  by  the  force  invested  in  the 
spring. 

The  motion  of  the  hands  may  be  called  a  phenomenon 
of  art,  but  the  case  is  similar  with  the  phenomena  of 
nature.  These  also  have  their  inner  mechanism,  and  their 
store  of  force  to  set  that  mechanism  going.  The  ultimate 
problem  of  physical  science  is  to  reveal  this  mechanism, 
to  discern  this  store,  and  to  show  that  from  the  combined 
action  of  both,  the  phenomena  of  which  they  constitute 
the  basis  must,  of  necessity,  flow. 

I  thought  an  attempt  to  give  you  even  a  brief  and 
sketchy  illustration  of  the  manner  in  which  scientific 
thinkers  regard  this  problem,  would  not  be  uninteresting 
to  you  on  the  present  occasion  ;  more  especially  as  it  will 
give  me  occasion  to  say  a  word  or  two  on  the  tendencies 
and  limits  of  modern  science  ;  to  point  out  the  region 
which  men  of  science  claim  as  their  own,  and  where  it  is 
mere  waste  of  time  to  oppose  their  advance ;  and  also  to 
define,  if  possible,  the  bourne  between  this  and  that  other 
region,  to  which  the  questionings  and  yearnings  of  the 
scientific  intellect  are  directed  in  vain. 

But  here  your  tolerance  will  be  needed.  It  was  the 
American  Emerson,  I  think,  who  said  that  it  is  hardly 
possible  to  state  any  truth  strongly,  without  apparent  in- 
justice to  some  other  truth.  Truth  is  often  of  a  dual 
character,  taking  the  form  of  a  magnet  with  two  poles ; 
and  many  of  the  differences  which  agitate  the  thinking 
part  of  mankind  are  to  be  traced  to  the  exclusiveness  with 
which  partisan  reasoners  dwell  upon  one  half  of  the 
duality,  in  forgetfulness  of  the  other.  The  proper  course 
appears  to  be  to  state  both  halves  strongly,  and  allow 


SCIENTIFIC  MATERIALISM.  413 

each  its  fair  share  in  the  formation  of  the  resultant  con- 
viction. But  this  waiting  for  the  statement  of  the  two 
sides  of  a  question  implies  patience.  It  implies  a  re- 
solution to  suppress  indignation,  if  the  statement  of  the 
one  half  should  clash  with  our  convictions  ;  and  to  repress 
equally  undue  elation,  if  the  half-statement  should  happen 
to  chime  in  with  our  views.  It  implies  a  determination 
to  wait  calmly  for  the  statement  of  the  whole,  before  we 
pronounce  judgment  in  the  form  of  either  acquiescence  or 
dissent. 

This  premised,  and  I  trust  accepted,  let  us  enter 
upon  our  task.  There  have  been  writers  who  affirmed  that 
the  pyramids  of  Egypt  were  natural  productions ;  and  in 
his  early  youth  Alexander  von  Humboldt  wrote  a  learned 
essay  with  the  express  object  of  refuting  this  notion.  We 
now  regard  the  pyramids  as  the  work  of  men's  hands, 
aided  probably  by  machinery  of  which  no  record  remains. 
We  picture  to  ourselves  the  swarming  workers  toiling  at 
those  vast  erections,  lifting  the  inert  stones,  and,  guided 
by  the  volition,  the  skill,  and  possibly  at  times  by  the  whip 
of  the  architect,  placing  them  in  their  proper  positions. 
The  blocks,  in  this  case,  were  moved  and  posited  by  a 
power  external  to  themselves,  and  the  final  form  of  the 
pyramid  expressed  the  thought  of  its  human  builder. 

Let  us  pass  from  this  illustration  of  constructive 
power  to  another  of  a  different  kind.  When  a  solution  of 
common  salt  is  slowly  evaporated,  the  water  which  holds 
the  salt  in  solution  disappears,  but  the  salt  itself  remains 
behind.  At  a  certain  stage  of  concentration  the  salt  can 
no  longer  retain  the  liquid  form ;  its  particles,  or  mole- 
cule', as  they  are  called,  begin  to  deposit  themselves  as 
minute  solids,  so  minute,  indeed,  as  to  defy  all  micro- 
scopic power.  As  evaporation  continues,  solidification 
goes  on,  and  we  finally  obtain,  through  the  clustering  to- 
gether of  innumerable  molecules,  a  finite  crystalline  ma  s 


414  FRAGMENTS   OF   SCIENCE. 

of  a  definite  form.  What  is  this  form  ?  It  sometimes 
seems  a  mimicry  of  the  architecture  of  Egypt.  We  have 
little  pyramids  built  by  the  salt,  terrace  above  terrace 
from  base  to  apex,  forming  a  series  of  steps,  resembling 
those  up  which  the  Egyptian  traveller  is  dragged  by  his 
guides.  The  human  mind  is  as  little  disposed  to  look  un- 
questioning at  these  pyramidal  salt-crystals,  as  to  look  at 
the  pyramids  of  Egypt,  without  enquiring  whence  they 
came.  How,  then,  are  those  salt-pyramids  built  up  ? 

Guided  by  analogy,  you  may,  if  you  like,  suppose  that, 
swarming  among  the  constituent  molecules  of  the  salt, 
there  is  an  invisible  population,  controlled  and  coerced  by 
some  invisible  master,  and  placing  the  atomic  blocks  in 
their  positions.  This,  however,  is  not  the  scientific  idea, 
nor  do  I  think  your  good  sense  will  accept  it  as  a  likely 
one.  The  scientific  idea  is,  that  the  molecules  act  upon 
each  other  without  the  intervention  of  slave  labour ;  that 
they  attract  each  other,  and  repel  each  other,  at  certain 
definite  points,  or  poles,  and  in  certain  definite  directions ; 
and  that  the  pyramidal  form  is  the  result  of  this  play  of 
attraction  and  repulsion.  While,  then,  the  blocks  of 
Egypt  were  laid  down  by  a  power  external  to  themselves, 
these  molecular  blocks  of  salt  are  self-posited,  being  fixed 
in  their  places  by  the  forces  with  which  they  act  upon 
each  other. 

I  take  common  salt  as  an  illustration,  because  it  is  so 
familiar  to  us  all ;  but  any  other  crystalline  substance 
would  answer  my  purpose  equally  well.  Everywhere,  in 
fact,  throughout  inorganic  nature,  we  have  this  formative 
power,  as  Fichte  would  call  it — this  structural  energy 
ready  to  come  into  play,  and  build  the  ultimate  particles 
of  matter  into  definite  shapes.  The  ice  of  our  winters, 
and  of  our  polar  regions,  is  its  handiwork,  and  so  also 
are  the  quartz,  felspar,  and  mica  of  our  rockg.  Our  chalk- 
beds  are  for  the  most  part  composed  of  minute  shells, 


SCIENTIFIC   MATERIALISM.  415 

which  are  also  the  product  of  structural  energy ;  but 
behind  the  shell,  as  a  whole,  lies  a  more  remote  and  subtle 
formative  act.  These  shells  are  built  up  of  little  crystals 
of  calc-spar,  and,  to  form  these  crystals,  the  structural  force 
had  to  deal  with  the  intangible  molecules  of  carbonate  of 
lime.  This  tendency  on  the  part  of  matter  to  organise 
itself,  to  grow  into  shape,  to  assume  definite  forms  in 
obedience  to  the  definite  action  of  force,  is,  as  I  have 
said,  all-pervading.  It  is  in  the  ground  on  which  you 
tread,  in  the  water  you  drink,  in  the  air  you  breathe. 
Incipient  life,  as  it  were,  manifests  itself  throughout  the 
whole  of  what  we  call  inorganic  nature. 

The  forms  of  the  minerals  resulting  from  this  play  of 
polar  forces  are  various,  and  exhibit  different  degrees  of 
complexity.  Men  of  science  avail  themselves  of  all 
possible  means  of  exploring  their  molecular  architecture. 
For  this  purpose  they  employ  in  turn,  as  agents  of  ex- 
ploration, light,  heat,  magnetism,  electricity,  and  sound. 
Polarised  light  is  especially  useful  and  powerful  here.  A 
beam  of  such  light,  when  sent  in  among  the  molecules  of 
a  crystal,  is  acted  on  by  them,  and  from  this  action  we 
infer  with  more  or  less  clearness  the  manner  in  which 
the  molecules  are  arranged.  That  differences,  for  ex- 
ample, exist  between  the  inner  structure  of  rock-salt  and 
crystallised  sugar  or  sugar-candy,  is  thus  strikingly  re- 
vealed. These  actions  often  display  themselves  in  chro- 
matic phenomena  of  great  splendour,  the  play  of  mole- 
cular force  being  so  regulated  as  to  remove  some  of  the 
coloured  constituents  of  white  light,  leaving  others  with 
increased  intensity  behind. 

And  now  let  us  pass  from  what  we  are  accustomed  to 
regard  as  a  dead  mineral,  to  a  living  grain  of  corn.  When 
this  is  examined  by  polarised  light,  chromatic  phenomena 
similar  to  those  noticed  in  crystals  are  observed.  And 
why  ?  Because  the  architecture  of  the  grain  resembles  the 


416  FKAGMENTS   OF   SCIENCE. 

architecture  of  the  crystal.  In  the  grain  also  the  mole- 
cules are  set  in  definite  positions,  and  in  accordance  with 
their  arrangement  they  act  upon  the  light.  But  what 
has  built  together  the  molecules  of  the  corn  ?  Kegarding 
crystalline  architecture,  I  have  already  said  that  you  may, 
if  you  please,  consider  the  atoms  and  molecules  to  bo 
placed  in  position  by  a  power  external  to  themselves. 
The  same  hypothesis  is  open  to  you  now.  But  if  in  the 
case  of  crystals  you  have  rejected  this  notion  of  an  external 
architect,  I  think  you  are  bound  to  reject  it  now,  and  to 
conclude  that  the  molecules  of  the  corn,  also,  are  posited 
by  the  forces  with  which  they  act  upon  each  other.  It 
would  be  poor  philosophy  to  invoke  an  external  agent 
in  the  one  case,  and  to  reject  it  in  the  other. 

Instead  of  cutting  our  grain  of  corn  into  slices  and 
subjecting  it  to  the  action  of  polarised  light,  let  us  place 
it  in  the  earth,  and  subject  it  to  a  certain  degree  of 
warmth.  In  other  words,  let  the  molecules,  both  of  the 
corn  and  of  the  surrounding  earth,  be  kept  in  that  state 
of  agitation  which  we  call  heat.  Under  these  circum- 
stances, the  grain  and  the  substances  which  surround  it 
interact,  and  a  definite  molecular  architecture  is  the  result. 
A  bud  is  formed ;  this  bud  reaches  the  surface,  where 
it  is  exposed  ti  the  sun's  rays,  which  are  also  to  be 
regarded  as  a  kind  of  vibratory  motion.  And  as  the 
motion  of  common  heat,  with  which  the  grain  and  the 
substances  surrounding  it  were  first  endowed,  enabled  the 
grain  and  these  substances  to  exercise  their  mutual  attrac- 
tions and  repulsions,  and  thus  to  coalesce  in  definite  forms, 
so  the  bpecific  motion  of  the  sun's  rays  now  enables  the  green 
bud  to  feed  upon  the  carbonic  acid  and  the  aqueous  vapour 
of  the  air.  The  bud  appropriates  those  constituents  of 
both  for  which  it  has  an  elective  attraction,  and  permits 
the  other  constituent  to  resume  its  place  in  the  atmosphere. 
Thus  the  architecture  is  carried  on.  Forces  are  active  at 


SCIENTIFIC  MATERIALISM.  417 

the  root,  forces  are  active  in  the  blade,  the  matter  of  the 
earth  and  the  matter  of  the  atmosphere  are  drawn  towards 
the  root  and  blade,  and  the  plant  augments  in  size.  We 
have  in  succession  the  stalk,  the  ear,  the  full  corn  in  the 
ear ;  the  cycle  of  molecular  action  being  completed  by  the 
production  of  grains,  similar  to  that  with  which  the  process 
began. 

Now  there  is  nothing  in  this  process  which  necessarily 
eludes  the  conceptive  or  imagining  power  of  the  human 
mind.  An  intellect  the  same  in  kind  as  our  own  would, 
if  only  sufficiently  expanded,  be  able  to  follow  the  whole 
pi-ocess  from  beginning  to  end.  It  would  see  every  mole- 
cule placed  in  its  position  by  the  specific  attractions  and 
repulsions  exerted  between  it  and  other  molecules,  the 
whole  process,  and  its  consummation,  being  an  instance  of 
the  play  of  molecular  force.  Given  the  grain  and  its 
environment,  the  purely  human  intellect  might,  if  suffi- 
ciently expanded,  trace  out  a  priori  every  step  of  the 
process  of  growth,  and,  by  the  application  of  purely 
mechanical  principles,  demonstrate  that  the  cycle  must 
end,  as  it  is  seen  to  end,  in  the  reproduction  of  forms  like 
that  with  which  it  began.  A  necessity  rules  here,  similar 
to  that  which  rules  the  planets  in  their  circuits  round  the 
sun. 

You  will  notice  that  I  am  stating  the  truth  strongly, 
as  at  the  beginning  we  agreed  it  should  be  stated.  But  I 
must  go  still  further,  and  affirm  that  in  the  eye  of  science 
the  animal  body  is  just  as  much  the  product  of  molecular 
force  as  the  stalk  and  ear  of  corn,  or  as  the  crystal  of  salt 
or  sugar.  Many  of  the  parts  of  the  body  are  obviously 
mechanical.  Take  the  human  heart,  for  example,  with  its 
system  of  valves,  or  take  the  exquisite  mechanism  of  the 
eye  or  hand.  Animal  heat,  moreover,  is  the  same  in  kind 
as  the  heat  of  a  fire,  being  produced  by  the  same  chemical 
process.  Animal  motion,  too,  is  as  directly  derived  from 


418  FRAGMENTS   OF   SCIENCE. 

the  food  of  the  animal,  as  the  motion  of  Trevethyck's 
walking-engine  from  the  fuel  in  its  furnace.  As  regards 
matter,  the  animal  body  creates  nothing  ;  as  regards  force, 
it  creates  nothing.  Which  of  you  by  taking  thought  can 
add  one  cubit  to  his  stature  ?  All  that  has  been  said, 
then,  regarding  the  plant,  may  be  restated  with  regard  to 
the  animal.  Every  particle  that  enters  into  the  composi- 
tion of  a  muscle,  a  nerve,  or  a  bone,  has  been  placed  in 
its  position  by  molecular  force.  And  unless  the  existence 
of  law  in  these  matters  be  denied,  and  the  element  of 
caprice  introduced,  we  must  conclude  that,  given  the  re- 
lation of  any  molecule  of  the  body  to  its  environment, 
its  position  in  the  body  might  be  determined  mathe- 
matically. Our  difficulty  is  not  with  the  quality  of  the 
problem,  but  with  its  complexity ;  and  this  difficulty 
might  be  met  by  the  simple  expansion  of  the  faculties  we 
now  possess.  Given  this  expansion,  with  the  necessary 
molecular  data,  and  the  chick  might  be  deduced  as 
rigorously  and  as  logically  from  the  egg,  as  the  existence 
of  Neptune  from  the  disturbances  of  Uranus,  or  as  conical 
refraction  from  the  undulatory  theory  of  light. 

You  see  I  am  not  mincing  matters,  but  avowing 
nakedly  what  many  scientific  thinkers  more  or  less  dis- 
tinctly believe.  The  formation  of  a  crystal,  a  plant,  or 
an  animal,  is,  in  their  eyes,  a  purely  mechanical  problem, 
which  differs  from  the  problems  of  ordinary  mechanics,  in 
the  smallness  of  the  masses,  and  the  complexity  of  the 
processes  involved.  Here  you  have  one  half  of  our  dual 
truth ;  let  us  now  glance  at  the  other  half.  Associated 
with  this  wonderful  mechanism  of  the  animal  body  we 
have  phenomena  no  less  certain  than  those  of  physics,  but 
between  which  and  the  mechanism  we  discern  no  neces- 
sary connection.  A  man,  for  example,  can  say  '  I  feel, 
*  I  think,'  '  I  love ; '  but  how  does  consciousness  infuse 
itself  into  the  problem  ?  The  human  brain  is  said  to  be 


SCIENTIFIC  MATERIALISM.  419 

the  organ  of  thought  and  feeling  :  when  we  are  hurt,  the 
brain  feels  it ;  when  we  ponder,  it  is  the  brain  that  thinks ; 
when  our  passions  or  affections  are  excited,  it  is  through 
the  instrumentality  of  the  brain.  Let  us  endeavour  to 
be  a  little  more  precise  here.  I  hardly  imagine  there  exists 
a  profound  scientific  thinker,  who  has  reflected  upon  the 
subject,  unwilling  to  admit  the  extreme  probability  of  the 
hypothesis,  that  for  every  fact  of  consciousness,  whether 
in  the  domain  of  sense,  of  thought,  or  of  emotion,  a 
definite  molecular  condition,  of  motion  or  structure,  is  set 
up  in  the  brain ;  or  who  would  be  disposed  even  to  deny 
that  if  the  motion,  or  structure,  be  induced  by  internal 
causes  instead  of  external,  the  effect  on  consciousness  will 
be  the  same  ?  Let  any  nerve,  for  example,  be  thrown  by 
morbid  action  into  the  precise  state  of  motion  which 
would  be  communicated  to  it  by  the  pulses  of  a  heated 
body,  surely  that  nerve  will  declare  itself  hot — the  mind 
will  accept  the  subjective  intimation  exactly  as  if  it  were 
objective.  The  retina  may  be  excited  by  purely  me- 
chanical means.  A  blow  on  the  eye  causes  a  luminous 
flash,  and  the  mere  pressure  of  the  finger  on  the  external 
ball  produces  a  star  of  light,  which  "Newton  compared  to 
the  circles  on  a  peacock's  tail.  Disease  makes  people 
see  visions  and  dream  dreams  ;  but,  in  all  such  cases, 
could  we  examine  the  organs  implicated,  we  should,  on 
philosophical  grounds,  expect  to  find  them  in  that  pre- 
cise molecular  condition  which  the  real  objects,  if  present, 
would  superinduce. 

The  relation  of  physics  to  consciousness  being  thus 
invariable,  it  follows  that,  given  the  state  of  the  brain, 
the  corresponding  thought  or  feeling  might  be  inferred: 
or,  given  the  thought  or  feeling,  the  corresponding  state 
of  the  brain  might  be  inferred.  But  how  inferred  ?  It 
would  be  at  bottom  not  a  case  of  logical  inference  at  all, 
but  of  empirical  association.  You  may  reply,  that  many 


420  FRAGMENTS   OF   SCIENCE. 

of  the  inferences  of  science  are  of  this  character — the  in- 
ference, for  example,  that  an  electric  current,  of  a  given 
direction,  will  deflect  a  magnetic  needle  in  a  definite  way. 
But  the  cases  differ  in  this,  that  the  passage  from  the 
current  to  the  needle,  if  not  demonstrable,  is  thinkable, 
and  that  we  entertain  no  doubt  as  to  the  final  mechanical 
solution  of  the  problem.  But  the  passage  from  the  physics 
of  the  brain  to  the  corresponding  facts  of  consciousness  is 
unthinkable.  Granted  that  a  definite  thought,  and  a  defi- 
nite molecular  action  in  the  brain,  occur  simultaneously; 
we  do  not  possess  the  intellectual  organ,  nor  apparently 
any  rudiment  of  the  organ,  which  would  enable  us  to  pass, 
by  a  process  of  reasoning,  from  the  one  to  the  other. 
They  appear  together,  but  we  do  not  know  why.  Were 
our  minds  and  senses  so  expanded,  strengthened,  and 
illuminated,  as  to  enable  us  to  see  and  feel  the  very  mole- 
cules of  the  brain ;  were  we  capable  of  following  all  their 
motions,  all  their  groupings,  all  their  electric  discharges, 
if  such  there  be ;  and  were  we  intimately  acquainted  with 
the  corresponding  states  of  thought  and  feeling,  we  should 
be  as  far  as  ever  from  the  solution  of  the  problem,  '  How 
are  these  physical  processes  connected  with  the  facts  of 
consciousness  ? '  The  chasm  between  the  two  classes  of 
phenomena  would  still  remain  intellectually  impassable. 
Let  the  consciousness  of  love,  for  example,  be  associated 
with  a  right-handed  spiral  motion  of  the  molecules  of  the 
brain,  and  the  consciousness  of  hate  with  a  left-handed 
spiral  motion.  We  should  then  know,  when  we  love,  that 
the  motion  is  in  one  direction,  and,  when  we  hate,  that  the 
motion  is  in  the  other ;  but  the  '  WHY  ? '  would  remain  as 
unanswerable  as  before. 

In  affirming  that  the  growth  of  the  body  is  mechanical, 
and  that  thcright,  as  exercised  by  us,  has  its  correlative 
in  the  physics  of  the  brain,  I  think  the  position  of  the 
'  Materialist '  is  stated,  as  far  as  that  position  is  a  tenable 


SCIENTIFIC  MATEEIALISM.  421 

one.  I  think  the  materialist  will  be  able  finally  to  main- 
tain this  position  against  all  attacks  ;  but  I  do  not  think, 
in  the  present  condition  of  the  human  mind,  that  he  can 
pass  beyond  this  position.  I  do  not  think  he  is  entitled 
to  say  that  his  molecular  groupings,  and  motions,  explain 
everything.  In  reality  they  explain  nothing.  The 
utmost  he  can  affirm  is  the  association  of  two  classes  of 
phenomena,  of  whose  real  bond  of  union  he  is  in  absolute 
ignorance.  The  problem  of  the  connection  of  body  and 
soul  is  as  insoluble,  in  its  modern  form,  as  it  was  in  the 
pre-scientific  ages.  Phosphorus  is  known  to  enter  into 
the  composition  of  the  human  brain,  and  a  trenchant 
German  writer  has  exclaimed,  '  Ohne  Phosphor,  kein 
Gedanke  ! '  That  may  or  may  not  be  the  case ;  but  even 
if  we  knew  it  to  be  the  case,  the  knowledge  would  not 
lighten  our  darkne  s.  On  both  sides  of  the  zone  here 
assigned  to  the  materialist  he  is  equally  helpless.  If  you 
ask  him  whence  is  this  '  Matter '  of  which  we  have  been 
discoursing — who  or  what  divided  it  into  molecules,  who 
or  what  impressed  upon  them  this  necessity  of  running 
into  organic  forms — he  has  no  answer.  Science  is  mute 
in  reply  to  these  questions.  But  if  the  materialist  is  con- 
founded and  science  rendered  dumb,  who  else  is  prepared 
with  a  solution?  To  whom  has  this  arm  of  the  Lord 
been  revealed  ?  Let  us  lower  our  heads,  and  acknowledge 
our  ignorance,  priest  and  philosopher,  one  and  all. 

Perhaps  the  mystery  may  resolve  itself  into  knowledge 
at  some  future  day.  The  process  of  things  upon  this  earth 
has  been  one  of  amelioration.  It  is  a  long  way  from  the 
Iguanodon  and  his  contemporaries,  to  the  President  and 
Members  of  the  British  Association.  And  whether  we 
regard  the  improvement  from  the  scientific  or  from  the 
theological  point  of  view — as  the  result  of  progressive 
development,  or  of  successive  exhibitions  of  creative 
energy  — neither  view  entitles  us  to  assume  that  man's 


422  FRAGMENTS    OF   SCIENCE. 

present  faculties  end  the  series,  that  the  process  of 
amelioration  ends  with  him.  A  time  may  therefore  come 
when  this  ultra-scientific  region,  by  which  we  are  now 
enfolded,  may  offer  itself  to  terrestrial,  if  not  to  human, 
investigation.  Two-thirds  of  the  rays  emitted  by  the 
sun  fail  to  arouse  the  sense  of  vision.  The  rays  exist, 
but  the  visual  organ  requisite  for  their  translation  into 
Kght  does  not  exist.  And  so  from  this  region  of  dark- 
ness and  mystery  which  surrounds  us,  rays  may  now  be 
darting,  which  require  but  the  development  of  the  proper 
intellectual  organs  to  translate  them  into  knowledge 
as  far  surpassing  ours,  as  ours  surpasses  that  of  the  wallow- 
ing reptiles  which  once  held  possession  of  this  planet. 
Meanwhile  the  mystery  is  not  without  its  uses.  It  certainly 
may  be  made  a  power  in  the  human  soul ;  but  it  is  a 
power  which  has  feeling,  not  knowledge,  for  its  base.  It 
may  be,  will  be,  and  1  hope  is  turned  to  account,  both  in 
steadying  and  strengthening  the  intellect,  and  in  rescuing 
man  from  that  littleness  to  which,  in  the  struggle  for 
existence,  or  for  precedence  in  the  world,  he  is  continually 
prone. 


The  reader  who  honours  the  '  Belfast  Address '  with 
his  attention,  may  fitly  supplement  its  perusal  by  that  of 
the  foregoing  Fragment.  1875. 


rv. 

SCIENTIFIC   USE  OF  THE  IMAGINATION. 
1870. 

'Lastly,  physical  investigation, more  than  anything  besides,  helps  to  teach 
vs  the  actual  value  and  right  use  of  the  Imagination — of  that  wondrous 
faculty,  which,  left  to  ramble  uncontrolled,  leads  us  astray  into  a  wUdern>ss 
of  perplexities  and  errors,  a  land  of  mists  and  shadows  ;  but  which,  properly 
controlled  by  experience  and  reflection,  becomes  the  noblest  attribute  of  man  ; 
the  source  of  poetic  genius,  the  instrument  of  discovery  in  Science,  without  the 
aid  of  which  Newton  would  never  have  invented  fluxions^  nor  Davy  have  de- 
composed the  earths  and  alkalies,  nor  would  Columbus  have  found  another 
Continent! — Address  to  the  Koyal  Society  by  its  President  Sir  Benjamin 
Brodie,  November  30,  1859. 

I  CARRIED  with  me  to  the  Alps  this  year  the  heavy 
burden  of  this  evening's  work.  In  the  way  of  new 
investigation  I  had  nothing  complete  enough  to  be  brought 
before  you ;  so  all  that  remained  to  me  was  to  fall  back 
upon  such  residues  as  could  be  found  in  the  depths  of  con- 
sciousness, and  out  of  them  to  spin  the  fibre,  and  weave  the 
web,  of  this  discourse.  Save  from  memory  I  had  no  direct 
aid  upon  the  mountains ;  but  to  spur  up  the  emotions, 
on  which  so  much  depends,  as  well  as  to  nourish  indirectly 
the  intellect  and  will,  I  took  with  me  four  works,  comprising 
two  volumes  of  poetry,  Goethe's  *  Farbenlehre,'  and  the 
work  on  '  Logic '  recently  published  by  Mr.  Alexander 
Bain. 

The  spur,  however,  was  no  match  for  the  integu- 
ment of  dulness  it  had  to  pierce.  In  Goethe,  so 
noble  otherwise,  I  chiefly  noticed  the  self-inflicted  hurts 
of  genius,  as  it  broke  in  vain  against  the  philosophy  of 


t24  FKAGMENTS   OF   SCIENCE. 

Newton.  For  a  time,  Mr.  Bain  became  my  principal 
companion.  I  found  him  learned  and  practical,  shining 
generally  with  a  dry  light,  but  exhibiting  at  times  a  flush 
of  emotional  strength,  which  proved  that  even  logicians 
share  the  common  fire  of  humanity.  He  interested  me 
most  when  he  became  the  mirror  of  my  own  condition 
Neither  intellectually  nor  socially  is  it  good  for  man  to 
be  alone,  and  the  griefs  of  thought  are  more  patiently 
borne  when  we  find  that  they  have  been  experienced  by 
another.  From  certain  passages  in  his  book  I  could  infer 
that  Mr.  Bain  was  no  stranger  to  such  sorrows.  Take 
this  as  an  illustration.  Speaking  of  the  ebb  of  intellec- 
tual force,  which  we  all  from  time  to  time  experience, 
Mr.  Bain  says :  '  The  uncertainty  where  to  look  for  the 
next  opening  of  discovery  brings  the  pain  of  conflict 
and  the  debility  of  indecision.'  These  words  have  in 
them  the  true  ring  of  personal  experience.  The  action  of 
the  investigator  is  periodic.  He  grapples  with  a  subject 
of  enquiry,  wrestles  with  it,  overcomes  it,  exhausts,  it  may 
be,  both  himself  and  it  for  the  time  being.  He  breathes 
a  space,  and  then  renews  the  struggle  in  another  field. 
Now  this  period  of  halting  between  two  investigations  is 
not  always  one  of  pure  repose.  It  is  often  a  period  of 
doubt  and  discomfort — of  gloom  and  ennui.  '  The  un- 
certainty where  to  look  for  the  next  opening  of  discovery 
brings  the  pain  of  conflict  and  the  debility  of  indecision.' 
Such  was  my  precise  condition  in  the  Alps  this  year ;  and 
it  was  under  these  evil  circumstances  that  I  had  to  equip 
myself  for  the  hour  and  the  ordeal  that  are  now  come. 

Gladly,  however,  as  I  should  have  seen  this  duty  in 
other  hands,  it  was  not  to  be  evaded.  In  some  fashion 
or  other — on  the  higher  levels  of  thought,  or  on  the  flats 
of  common-place — the  task  had  to  be  accomplished.  My 
case  for  a  time  resembled  that  of  a  sick  doctor  who  had 
forgotten  his  art,  and  who  sorely  needed  the  prescription 


SCIENTIFIC   USE   OP   THE   IMAGINATION.  425 

of  a  friend.  Mr.  Bain  wrote  one  for  me.  '  Your  present 
knowledge,'  he  said,  '  must  forge  the  links  of  connection 
between  what  has  been  already  achieved  and  what  is  now 
required. ' '  In  these  words  he  admonished  me  to  review 
the  past,  and  recover  from  it  the  broken  ends  of  former 
investigations.  I  tried  to  do  so.  Previous  to  going  to 
Switzerland  I  had  been  thinking  much  of  light  and  heat, 
of  organic  germs,  atoms,  comets,  and  skies.  With  one  or 
another  of  these  I  now  sought  to  re-form  an  alliance,  and 
finally  succeeded  in  establishing  a  kind  of  cohesion 
between  thought  and  Light. 

The  disciplines  of  common  life  are,  in  great  part, 
exercises  in  the  relations  of  space,  or  in  the  mental 
grouping  of  bodies  in  space  ;  and,  by  such  exercises,  the 
mind  is,  to  some  extent,  prepared  for  the  reception  of 
physical  conceptions.  Assuming  this  preparation  on  your 
part,  the  wish  grew  within  me  to  trace,  and  to  enable  you 
to  trace,  some  of  the  more  occult  operations  of  the  agent 
just  referred  to.  I  wished,  if  possible,  to  take  you  beyond 
the  boundary  of  mere  observation,  into  a  region  where 
things  are  intellectiially  discerned,  and  to  show  you  there 
the  hidden  mechanism  of  optical  action. 

But  how  are  those  hidden  things  to  be  revealed  ? 
How  are  we  to  lay  hold  of  the  physical  basis  of  light, 
since,  like  that  of  life  itself,  it  lies  entirely  without  the 
domain  of  the  senses?  Philosophers  may  be  right  in 
affirming  that  we  cannot  transcend  experience ;  but  we 
can,  at  all  events,  carry  it  a  long  way  from  its  origin. 
We  can  also  magnify,  diminish,  qualify,  and  combine  ex- 
periences, so  as  to  render  them  fit  for  purposes  entirely 
new.  Urged  to  the  attempt  by  sensible  phenomena,  we 
find  ourselves  gifted  with  the  power  of  forming  mental 
images  of  the  ultra-sensible  ;  and  by  this  power,  when 
duly  chastened  and  controlled,  we  can  lighten  the  dark« 

1  '  luduction,'  p.  422. 


120  FEAGMENTS   OF  SCIENCE. 

ness  which  surrounds  the  world  of  the  senses.  There 
are  Tories  even  in  science  who  regard  Imagination  as  a 
faculty  to  be  feared  and  avoided  rather  than  employed. 
They  have  observed  its  action  in  weak  vessels,  and  are 
unduly  impressed  by  its  disasters.  But  they  might  with 
equal  justice  point  to  exploded  boilers  as  an  argument 
against  the  use  of  steam.  Nourished  by  knowledge 
patiently  won  ;  bounded  and  conditioned  by  co-operant 
Keason ;  imagination  becomes  the  prime  mover  of  the 
physical  discoverer.  Newton's  passage  from  a  falling 
apple  to  a  falling  moon  was,  at  the  outset,  a  leap  of  the 
prepared  imagination.  In  Faraday  the  exercise  of  this 
faculty  preceded  all  his  experiments,  and  its  function  has 
been  impressively  set  forth  by  Brodie.1  When  William 
Thomson  tries  to  place  the  ultimate  particles  of  matter 
between  his  compass  points,  and  to  apply  to  them  a  scale 
of  millimetres,  it  is  an  act  of  the  scientific  imagination. 
And  in  much  that  has  been  recently  said  about  protoplasm 
and  life  we  have  the  outgoings  of  this  faculty  guided  and 
controlled  by  the  known  analogies  of  science.  In  fact, 
without  this  power,  our  knowledge  of  nature  would  be 
a  mere  tabulation  of  co-existences  and  sequences.  We 
should  still  believe  in  the  succession  of  day  and  night,  of 
summer  and  winter ;  but  the  soul  of  Force  would  be  dis- 
lodged from  our  universe ;  causal  relations  would  disappear, 
and  with  them  that  science  which  is  now  binding  the 
parts  of  nature  to  an  organic  whole. 

I  should  like  to  illustrate  by  a  few  simple  instances  the 
use  that  scientific  men  have  already  made  of  this  power  of 
imagination,  and  to  indicate  afterwards  some  of  the  further 
uses  that  they  are  likely  to  make  of  it.  Let  us  begin  with 
the  rudimentary  experiences.  Observe  the  falling  of  heavy 
rain-drops  into  a  tranquil  pond.  Each  drop  as  it  strikes 

1  At  the  outset  of  this  discourse. 


SCIENTIFIC  USE   OF   THE   IMAGINATION.  427 

the  water  becomes  a  centre  of  disturbance,  from  which  a 
series  of  ring-ripples  expand  outwards.  Gravity  and  inertia 
are  the  agents  by  which  this  wave-motion  is  produced,  and 
a  rough  experiment  will  suffice  to  show  that  the  rate  of 
propagation  does  not  amount  to  a  foot  a  second.  A  series 
of  slight  mechanical  shocks  is  experienced  by  a  body  plunged 
in  the  water,  as  the  wavelets  reach  it  in  succession.  But  a 
finer  motion  is  at  the  same  time  set  up  and  propagated. 
If  the  head  and  ears  be  immersed  in  the  water,  as  in  an 
experiment  of  Franklin's,  the  shock  of  the  drop  is  commu- 
nicated to  the  auditory  nerve — the  tick  of  the  drop  is  heard. 
Now,  this  sonorous  impulse  is  propagated,  not  at  the  rate 
of  a  foot,  but  at  the  rate  of  4,700  feet  a  second.  In  this 
case  it  is  not  the  gravity  but  the  elasticity  of  the  water 
that  is  the  urging  force.  Every  liquid  particle  pushed 
against  its  neighbour  delivers  up  its  motion  with  extreme 
rapidity,  and  the  pulse  is  propagated  as  a  thrill.  The  in- 
compressibility  of  water,  as  illustrated  by  the  famous 
Florentine  experiment?  is  a  measure  of  its  elasticity  ;  and 
to  the  possession  of  this  property,  in  so  high  a  degree,  the 
rapid  transmission  of  a  sound-pulse  through  water  is  to  be 
ascribed. 

But  water,  as  you  know,  is  not  necessary  to  the  conduc- 
tion of  sound  ;  air  is  its  most  common  vehicle.  And  you 
know  that  when  the  air  possesses  the  particular  density 
and  elasticity  corresponding  to  the  temperature  of  freezing 
water,  the  velocity  of  sound  in  it  is  1,090  feet  a  second. 
It  is  almost  exactly  one-fourth  of  the  velocity  in  water ; 
the  reason  being  that  though  the  greater  weight  of  the 
water  tends  to  diminish  the  velocity,  the  enormous  mole- 
cular elasticity  of  the  liquid  far  more  than  atones  for  the 
disadvantage  due  to  weight.  By  various  contrivances  we  can 
compel  the  vibrations  of  the  air  to  declare  themselves ;  we 
know  the  length  and  frequency  of  the  sonorous  waves,  and  we 
have  also  obtained  great  mastery  over  the  various  methods 


428  FRAGMENTS   OF   SCIENCE. 

by  which  the  air  is  thrown  into  vibration.  We  know  the 
phenomena  and  laws  of  vibrating  rods,  of  organ-pipes, 
strings,  membranes,  plates,  and  bells.  \Ve  can  abolish 
one  sound  by  another.  We  know  the  physical  meaning  of 
music  and  noise,  of  harmony  and  discord.  In  short,  as 
regards  sound  in  general,  we  have  a  very  clear  notion  of 
the  external  physical  processes  which  correspond  to  our 
sensations. 

In  the  phenomena  of  sound,  we  travel  a  very  little  way 
from  downright  sensible  experience.  Still  the  imagination 
is  to  some  extent  exercised.  The  bodily  eye,  for  example, 
cannot  see  the  condensations  and  rarefactions  of  the  waves 
of  sound.  We  construct  them  in  thought,  and  we  believe 
as  firmly  in  their  existence  as  in  that  of  the  air  itself. 
But  now  our  experience  is  to  be  carried  into  a  new  region, 
where  a  new  use  is  to  be  made  of  it.  Having  mastered 
the  cause  and  mechanism  of  sound,  we  desire  to  know  the 
cause  and  mechanism  of  light.  We  wish  to  extend  our 
enquiries  from  the  auditory  to  the  *>ptic  nerve.  There  is 
in  the  human  intellect  a  power  of  expansion — I  might 
almost  call  it  a  power  of  creation — which  is  brought  into 
play  by  the  simple,  brooding  upon  facts.  The  legend  of 
the  Spirit  brooding  over  chaos  may  have  originated  in  a 
knowledge  of  this  power.  In  the  case  now  before  us  it 
has  manifested  itself  by  transplanting  into  space,  for  the 
purposes  of  light,  an  adequately  modified  form  of  the 
mechanism  of  sound.  We  know  intimately  whereon  the 
velocity  of  sound  depends.  When  we  lessen  the  density 
of  a  medium,  and  preserve  its  elasticity  constant,  we  aug- 
ment the  velocity.  When  we  heighten  the  elasticity,  and 
keep  the  density  constant,  we  also  augment  the  velocity. 
A  small  density,  therefore,  and  a  great  elasticity,  are  the 
two  things  necessary  to  rapid  propagation.  Now  light  is 
known  to  move  with  the  astounding  velocity  of  186,000 
miles  a  second.  How  is  such  a  velocity  to  be  obtained  ? 


SCIENTIFIC  USE   OF   THE   IMAGINATION.  429 

By  boldly  diffusing  in  space  a  medium  of  the  requisite 
tenuity  and  elasticity. 

Let  us  make  such  a  medium  our  starting-point,  and, 
endowing  it  with  one  or  two  other  necessary  qualities, 
let  us  handle  it  in  accordance  with  strict  mechanical  laws. 
Let  us  then  carry  our  results  from  the  world  of  theory 
into  the  world  of  sense,  and  see  whether  our  deductions 
do  not  issue  in  the  very  phenomena  of  light  which  ordi- 
nary knowledge  and  skilled  experiment  reveal.  If  in  all 
the  multiplied  varieties  of  these  phenomena,  including 
those  of  the  most  remote  and  entangled  description,  this 
fundamental  conception  always  brings  us  face  to  face  with 
the  truth  ;  if  no  contradiction  to  our  deductions  from  it 
be  found  in  external  nature,  but  on  all  sides  agreement 
and  verification ;  if,  moreover,  as  in  the  case  of  Conical 
Eefraction  and  in  other  cases,  it  actually  forces  upon  our 
attention  phenomena  which  no  eye  had  previously  seen, 
and  which  no  mind  had  previously  imagined — such  a  con- 
ception must,  we  think,  be  something  more  than  a  mere 
figment  of  the  scientific  fancy.  In  forming  it,  that  com- 
posite and  creative  power,  in  which  reason  and  imagina- 
tion are  united,  has,  we  believe,  led  us  into  a  world  not 
less  real  than  that  of  the  senses,  and  of  which  the  world 
of  sense  itself  is  the  suggestion  and  justification. 

Far  be  it  from  me,  however,  to  wish  to  fix  you  immov- 
ably in  this  or  in  any  other  theoretic  conception.  With 
all  our  belief  of  it,  it  will  be  well  to  keep  the  theory  of 
a  luminiferous  aether  plastic  and  capable  of  change.  You 
may,  moreover,  urge  that,  although  the  phenomena  occur 
as  if  the  medium  existed,  the  absolute  demonstration  of 
its  existence  is  still  wanting.  Far  be  it  from  me  to  deny 
to  this  reasoning  such  validity  as  it  may  fairly  claim. 
Let  us  endeavour  by  means  of  analogy  to  form  a  fair 
estimate  of  its  force.  You  believe  that  in  society  you  are 
surrounded  by  reasonable  beings  like  yourself.  You  are, 


t30  FRAGMENTS   OF   SCIENCE. 

perhaps,  as  firmly  convinced  of  this  as  of  anything.  What 
is  your  warrant  for  this  conviction  ?  Simply  and  solely 
this  :  your  fellow-creatures  behave  as  if  they  were  reason- 
able ;  the  hypothesis,  for  it  is  nothing  more,  accounts  for 
the  facts.  To  take  an  eminent  example  :  you  believe  that 
our  President  is  a  reasonable  being.  Why  ?  There  is  no 
known  method  of  superposition  by  which  any  one  of  us 
can  apply  himself  intellectually  to  another,  so  as  to  de- 
monstrate coincidence  as  regards  the  possession  of  reason. 
If,  therefore,  you  hold  our  President  to  be  reasonable,  it 
is  because  he  behaves  as  if  he  were  reasonable.  As  in 
the  case  of  the  aether,  beyond  the  '  as  if  you  cannot  go. 
Nay,  I  should  not  wonder  if  a  close  comparison  of  the 
data  on  which  both  inferences  rest,  caused  many  respect- 
able persons  to  conclude  that  the  aether  had  the  best 
of  it. 

This  universal  medium,  this  light-aether  as  it  is  called, 
is  a  vehicle,  not  an  origin,  of  wave-motion.  It  receives 
and  transmits,  but  it  does  not  create.  Whence  does  it 
derive  the  motions  it  conveys  ?  For  the  most  part  from 
luminous  bodies.  By  this  motion  of  a  luminous  body  I 
do  not  mean  its  sensible  motion,  such  as  the  flicker  of  a 
candle,  or  the  shooting  out  of  red  prominences  from  the 
limb  of  the  sun.  I  mean  an  intestine  motion  of  the 
atoms  or  molecules  of  the  luminous  body.  But  here  a 
certain  reserve  is  necessary.  Many  chemists  of  the 
present  day  refuse  to  speak  of  atoms  and  molecules  as 
real  things.  Their  caution  leads  them  to  stop  short  of 
the  clear,  sharp,  mechanically  intelligible  atomic  theory 
enunciated  by  Dalton,  or  any  form  of  that  theory,  and  to 
make  the  doctrine  of  'multiple  proportions'  their  intel- 
lectual bourne.  I  respect  the  caution,  though  I  think  it 
is  here  misplaced.  The  chemists  who  recoil  from  these 
notions  of  atoms  and  molecules  accept,  without  hesitation, 
the  Undulatory  Theory  of  Light.  Like  you  and  me  they 


SCIENTIFIC  USE   OF   THE   IMAGINATION.  431 

one  and  all  believe  in  an  aether  and  its  light-producing 
waves.  Let  us  consider  what  this  belief  involves.  Bring 
your  imaginations  once  more  into  play,  and  figure  a  series 
of  sound-waves  passing  through  air.  Follow  them  up  to 
their  origin,  and  what  do  you  there  find?  A  definite, 
tangible,  vibrating  body.  It  may  be  the  vocal  chords  of 
a  human  being,  it  may  be  an  organ-pipe,  or  it  may  be  a 
stretched  string.  Follow  in  the  same  manner  a  train  of 
aether-waves  to  their  source ;  remembeiing  at  the  same 
time  that  your  aether  is  matter,  dense,  elastic,  and  capable 
of  motions  subject  to,  and  determined  by,  mechanical 
laws.  What  then  do  you  expect  to  find  as  the  source  of  a 
series  of  aether-waves  ?  Ask  your  imagination  if  it  will 
accept  a  vibrating  multiple  proportion — a  numerical  ratio 
in  a  state  of  oscillation  ?  I  do  not  think  it  will.  You 
cannot  crown  the  edifice  with  this  abstraction.  The  scien- 
tific imagination,  which  is  here  authoritative,  demands,  as 
the  origin  and  cause  of  a  series  of  aether-waves,  a  particle 
of  vibrating  matter  quite  as  definite,  though  it  may  be 
excessively  minute,  as  that  which  gives  origin  to  a  musical 
sound.  Such  a  particle  we  name  an  atom  or  a  molecule. 
I  think  the  intellect,  when  focussed  so  as  to  give  definition 
without  penumbral  haze,  is  sure  to  realise  this  image  at 
the  la«t. 

With  the  view  of  preserving  thought  continuous 
throughout  this  discourse,  and  of  preventing  either  failure 
of  knowledge,  or  of  memory,  from  causing  any  rent  in  our 
picture,  I  here  propose  to  run  rapidly  over  a  bit  of  ground 
which  is  probably  familiar  to  most  of  you,  but  which  I  am 
anxious  to  make  familiar  to  you  all.  The  waves  generated 
in  the  aether  by  the  swinging  atoms  of  luminous  bodies 
are  of  different  lengths  and  amplitudes.  The  amplitude 
is  the  width  of  swing  of  the  individual  particles  of  the 
waves.  In  water-waves  it  is  the  height  of  the  crest  above 
the  trough,  while  the  length  of  the  wave  is  the  distance 


432  FRAGMENTS    OF   SCIENCE. 

between  two  consecutive  crests.  The  aggregate  of  wavea 
emitted  by  the  sun  may  be  broadly  divided  into  two 
classes  :  the  one  class  competent,  the  other  incompetent, 
to  excite  vision.  But  the  light-producing  waves  differ 
markedly  among  themselves  in  size,  form,  and  force. 
The  length  of  the  largest  of  these  waves  is  about  twice 
that  of  the  smallest,  but  the  amplitude  of  the  largest  is 
probably  a  hundred  times  that  of  the  smallest.  Now  the 
force  or  energy  of  the  wave,  which,  expressed  with  refer- 
ence to  sensation,  means  the  intensity  of  the  light,  is 
proportional  to  the  square  of  the  amplitude.  Hence  the 
amplitude  being  one-hundredfold,  the  energy  of  the 
largest  light-giving  waves  would  be  ten-thousandfold  that 
of  the  smallest.  This  is  not  improbable.  I  use  these 
figures  not  with  a  view  to  numerical  accuracy,  but  to  give 
you  definite  ideas  of  the  differences  that  probably  exist 
among  the  light-giving  waves.  And  if  we  take  the  whole 
range  of  solar  radiation  into  account — its  non-visual  as 
well  as  its  visual  waves — I  think  it  probable  that  the 
force,  or  energy,  of  the  largest  wave  is  a  million  times 
that  of  the  smallest. 

Turned  into  their  equivalents  of  sensation,  the  dif- 
ferent light-waves  produce  different  colours.  Red,  for 
example,  is  produced  by  the  largest  waves,  violet  by  the 
smallest,  while  green  is  produced  by  a  wave  of  inter- 
mediate length  and  amplitude.  On  entering  from  air 
into  a  more  highly  refracting  substance,  such  as  glass  or 
water,  or  the  sulphide  of  carbon,  all  the  waves  are  re- 
tarded, but  the  smallest  ones  most.  This  furnishes  a 
means  of  separating  the  different  classes  of  waves  from 
each  other ;  in  other  words,  of  analysing  the  light.  Sent 
through  a  refracting  prism,  the  waves  of  the  sun  are 
turned  aside  in  different  degrees  from  their  direct  course, 
the  red  least,  the  violet  most.  They  are  virtually  pulled 
asunder,  and  they  paint  upon  a  white  screen  placed  to 


SCIENTIFIC  USE   OF   THE   IMAGINATION.  433 

receive  them  '  the  solar  spectrum.'  Strictly  speaking,  the 
spectrum  embraces  an  infinity  of  colours ;  but  the  limits  of 
language,  and  of  our  powers  of  distinction,  cause  it  to  be 
divided  into  seven  segments  :  red,  orange,  yellow,  green, 
blue,  indigo,  violet.  These  are  the  seven  primary  or  prism- 
atic colours. 

Separately,  or  mixed  in  various  proportions,  the  solar 
waves  yield  all  the  colours  observed  in  nature  and  em- 
ployed in  art.  Collectively,  they  give  us  the  impression 
of  whiteness.  Pure  unsifted  solar  light  is  white  ;  and,  if 
all  the  wave-constituents  of  such  light  be  reduced  in  the 
same  proportion,  the  light,  though  diminished  in  intensity, 
will  still  be  white.  The  whiteness  of  Alpine  snow  with 
the  sun  shining  upon  it,  is  barely  tolerable  to  the  eye. 
The  same  snow  under  an  overcast  firmament  is  still  white. 
Such  a  firmament  enfeebles  the  light  by  reflecting  it  up- 
wards ;  and  when  we  stand  above  a  cloud-field — on  an 
Alpine  summit,  for  instance,  or  on  the  top  of  Snowdon — 
and  see,  in  the  proper  direction,  the  sun  shining  on  tho 
clouds  below  us,  they  appear  dazzlingly  white.  Ordinary 
clouds,  in  fact,  divide  the  solar  light  impinging  on  them 
into  two  parts — a  reflected  part  and  a  transmitted  part,  in 
each  of  which  the  proportions  of  wave-motion  which  pro- 
duce the  impression  of  whiteness  are  sensibly  preserved. 

It  will  be  understood  that  the  condition  of  whiteness 
would  fail  if  all  the  waves  were  diminished  equally r,  or  by 
the  same  absolute  quantity.  They  must  be  reduced  pro- 
portionately, instead  of  equally.  If  by  the  act  of  reflec- 
tion the  waves  of  red  light  are  split  into  exact  halves, 
then,  to  preserve  the  light  white,  the  waves  of  yellow, 
orange,  green,  and  blue  must  also  be  split  into  exact  halves. 
In  short,  the  reduction  must  take  place,  not  by  absolutely 
equal  quantities,  but  by  equal  fractional  parts.  In 
white  light  the  preponderance,  as  regards  energy,  of  the 
larger  over  the  smaller  waves  must  always  be  immense. 


434  FRAGMENTS   OF   SCIENCE. 

Were  the  case  otherwise,  the  visual  correlative,  blue,  of 
the  smaller  waves  would  have  the  upper  hand  in  our 
sensations. 

Not  only  are  the  waves  of  aether  reflected  by  clouds, 
by  solids,  and  liquids,  but  when  they  pass  from  light  air 
to  dense,  or  from  dense  air  to  light,  a  portion  of  the  wave- 
motion  is  always  reflected.  Now  our  atmosphere  changes 
continually  in  density  from  top  to  bottom.  It  will  help 
our  conceptions  if  we  regard  it  as  made  up  of  a  series  of 
thin  concentric  layers,  or  shells  of  air,  each  shell  being  of 
the  same  density  throughout,  a  small  and  sudden  change 
of  density  occurring  in  passing  from  shell  to  shell.  Light 
would  be  reflected  at  the  limiting  surfaces  of  all  these 
shells,  and  their  action  would  be  practically  the  same  as 
that  of  the  real  atmosphere.  And  now  I  would  ask  your 
imagination  to  picture  this  act  of  reflection.  What  must 
become  of  the  reflected  light  ?  The  atmospheric  layers 
turn  their  convex  surfaces  towards  the  sun ;  they  are  so 
many  convex  mirrors  of  feeble  power ;  and  you  will  im- 
mediately perceive  that  the  light  regularly  reflected  from 
these  surfaces  cannot  reach  the  earth  at  all,  but  is  dis- 
persed in  space.  Light  thus  reflected  cannot  be  the  light 
of  the  sky. 

But,  though  the  sun's  light  is  not  reflected  in  this 
fashion  from  the  aerial  layers  to  the  earth,  there  is  indu- 
bitable evidence  to  show  that  the  light  of  our  firmament 
is  reflected  light.  Proofs  of  the  most  cogent  descriptor 
could  be  here  adduced ;  but  we  need  only  consider  that 
we  receive  light  at  the  same  time  from  all  parts  of  the 
hemisphere  of  heaven.  The  light  of  the  firmament  comes 
to  us  across  the  direction  of  the  solar  rays,  and  even 
against  the  direction  of  the  solar  rays ;  and  this  lateral 
and  opposing  rush  of  wave-motion  can  only  be  due  to 
the  rebound  of  the  waves  from  the  air  itself,  or  from 
something  suspended  in  the  air.  It  is  also  evident  that. 


SCIENTIFIC   USE   OF   THE   IMAGINATION.  435 

unlike  the  action  of  clouds,  the  solar  light  is  not  reflected 
by  the  sky  in  the  proportions  which  produce  white.  The 
sky  is  blue,  which  indicates  an  excess  of  the  shorter 
waves.  In  accounting  for  the  colour  of  the  sky,  the 
first  question  suggested  by  analogy  would  undoubtedly  be, 
Is  not  the  air  blue?  The  blueness  of  the  air  has,  in 
fact,  been  given  as  a  solution  of  the  blueness  of  the  sky. 
But  how,  if  the  air  be  blue,  can  the  light  of  sunrise  and 
sunset,  which  travels  through  vast  distances  of  air,  be 
yellow,  orange,  or  even  red  ?  The  passage  of  white  solar 
light  through  a  blue  medium  could  by  no  possibility  red- 
den the  light.  The  hypothesis  of  a  blue  air  is  therefore 
untenable.  In  fact  the  agent,  whatever  it  is,  which 
sends  us  the  light  of  the  sky,  exercises  in  so  doing  a 
dichroitic  action.  The  light  reflected  is  blue,  the  light 
transmitted  is  orange  or  red.  A  marked  distinction  is 
thus  exhibited  between  the  matter  of  the  sky,  and  that 
of  an  ordinary  cloud,  which  exercises  no  such  dichroitic 
action. 

By  the  scientific  use  of  the  imagination  we  may 
penetrate  this  mystery  also.  The  cloud  takes  no  note 
of  size  on  the  part  of  the  waves  of  aether,  but  reflects 
them  all  alike.  It  exercises  no  selective  action.  Now 
the  cause  of  this  may  be  that  the  cloud  particles  are  so 
large,  in  comparison  with  the  waves  of  aether,  as  to 
reflect  them  all  indifferently.  A  broad  cliff  reflects  an 
Atlantic  roller  as  easily  as  a  ripple  produced  by  a  sea- 
bird's  wing ;  and,  in  the  presence  of  large  reflecting  sur- 
faces, the  existing  differences  of  magnitude  among  the 
waves  of  aether  may  disappear.  But  supposing  the  re- 
flecting particles,  instead  of  being  very  large,  to  be  very 
small  in  comparison  with  the  size  of  the  waves.  In  this 
case,  instead  of  the  whole  wave  being  fronted  and  thrown 
back,  a  small  portion  only  is  shivered  off.  The  great 
mass  of  the  wave  passes  over  such  a  particle  without  re- 


436  FRAGMENTS   OP   SCIENCE. 

flection.  Scatter,  then,  a  handful  of  such  minute  foreign 
particles  in  our  atmosphere,  and  set  imagination  to  watch 
their  action  upon  the  solar  waves.  Waves  of  all  sizes 
impinge  upon  the  particles,  and  you  see  at  every  collision 
a  portion  of  the  impinging  wave  struck  off;  all  the  waves 
of  the  spectrum,  from  the  extreme  red  to  the  extreme  vio- 
let, being  thus  acted  upon. 

Eemembering  that  the  red  waves  stand  to  the  blue 
much  in  the  relation  of  billows  to  ripples,  we  have  to  con- 
sider whether  those  extremely  small  particles  are  com- 
petent to  scatter  all  the  waves  in  the  same  proportion.  If 
they  be  not — and  a  little  reflection  will  make  it  clear  that 
(.hey  are  not — the  production  of  colour  must  be  an  incident 
of  the  scattering.  Largeness  is  a  thing  of  relation ;  and 
the  smaller  the  wave,  the  greater  is  the  relative  size  of  any 
particle  on  which  the  wave  impinges,  and  the  greater  also 
the  ratio  of  the  scattered  portion  of  the  wave,  to  the  total 
wave.  A  pebble,  placed  in  the  way  of  the  ring-ripples 
produced  by  heavy  rain-drops  on  a  tranquil  pond,  will 
scatter  a  large  fraction  of  each  ripple,  while  the  fractional 
part  of  a  larger  wave  thrown  back  by  the  same  pebble 
might  be  infinitesimal.  Now  we  have  already  made  it 
clear  to  our  minds  that  to  preserve  the  solar  light  white,  its 
constituent  proportions  must  not  be  altered  ;  but  in  the 
act  of  division  performed  by  these  very  small  particles  the 
proportions  are  altered  ;  an  undue  fraction  of  the  smaller 
waves  is  scattered  by  the  particles,  and,  as  a  consequence 
in  the  scattered  light,  blue  will  be  the  predominant 
colour.  The  other  colours  of  the  spectrum  must,  to 
some  extent,  be  associated  with  the  blue.  They  are  not 
absent,  but  deficient.  We  ought,  in  fact,  to  have  them 
all,  but  in  diminishing  proportions,  from  the  violet  to 
the  red. 

We  have  here  presented  a  case  to  the  imagination,  and, 
assuming  the  undulatory  theory  to  be  a  reality,  we  have, 


SCIENTIFIC   USE   OF   THE   IMAGINATION.  437 

1  think,  fairly  reasoned  our  way  to  the  conclusion,  that 
were  particles,  small  in  comparison  to  the  size  of  the 
aether  waves,  sown  in  our  atmosphere,  the  light  scattered 
by  those  particles  would  be  exactly  such  as  we  observe  in 
our  azure  skies.  When  this  light  is  analysed,  all  the 
colours  of  the  spectrum  are  found,  and  they  are  found  in 
the  proportions  indicated  by  our  conclusion. 

Let  us  now  turn  our  attention  to  the  light  which 
passes  unscattered  among  the  particles.  How  must  it  be 
finally  affected  ?  By  its  successive  collisions  with  the 
particles  the  white  light  is  more  and  more  robbed  of  its 
shorter  waves  ;  it  therefore  loses  more  and  more  of  its 
due  proportion  of  blue.  The  result  may  be  anticipated. 
The  transmitted  light,  where  short  distances  are  involved, 
will  appear  yellowish.  But  as  the  sun  sinks  towards  the 
horizon  the  atmospheric  distances  increase,  and  conse- 
quently the  number  of  the  scattering  particles.  They 
abstract  in  succession  the  violet,  the  indigo,  the  blue,  and 
even  disturb  the  proportions  of  green.  The  transmitted 
light  under  such  circumstances  must  pass  from  yellow 
through  orange  to  red.  This  also  is  exactly  what  we  find 
in  nature.  Thus,  while  the  reflected  light  gives  us  at 
noon  the  deep  azure  of  the  Alpine  skies,  the  transmitted 
light  gives  us  at  sunset  the  warm  crimson  of  the  Alpine 
snows.  The  phenomena  certainly  occur  as  if  our 
atmosphere  were  a  medium  rendered  slightly  turbid  by 
the  mechanical  suspension  of  exceedingly  small  toreign 
particles. 

Here,  as  before,  we  encounter  our  sceptical  las  if.'  It 
is  one  of  the  parasites  of  science,  ever  at  hand,  and  ready 
to  plant  itself  and  sprout,  if  it  can,  on  the  weak  points  of 
our  philosophy.  But  a  strong  constitution  defies  the 
parasite,  and  in  our  case,  as  we  question  the  phenomena, 
probability  grows  like  growing  health,  until  in  the  one 
the  malady  of  doubt  is  completely  extirpated.  The  first 


438  FRAGMENTS   OF   SCIENCE. 

question  that  naturally  arises  is  this :  Can  small  particles 
he  really  proved  to  act  in  the  manner  indicated  ?  No 
douht  of  il  Each  one  of  you  can  submit  the  question  to 
an  experimental  test.  "Water  will  not  dissolve  resin,  but 
spirit  will  dissolve  it ;  and  when  spirit  holding  resin  in 
solution  is  dropped  into  water,  the  resin  immediately 
separates  in  solid  particles,  which  render  the  water  milky. 
The  coarseness  of  this  precipitate  depends  on  the  quantity 
of  the  dissolved  resin.  You  can  cause  it  to  separate  either 
in  thick  clots  or  in  exceedingly  fine  particles.  Professor 
Briicke  has  given  us  the  proportions  which  produce 
particles  particularly  suited  to  our  present  purpose.  One 
gramme  of  clean  mastic  is  dissolved  in  eighty-seven 
grammes  of  absolute  alcohol,  and  the  transparent  solution 
is  allowed  to  drop  into  a  beaker  containing  clear  water, 
kept  briskly  stirred.  An  exceedingly  fine  precipitate  is 
thus  formed,  which  declares  its  presence  by  its  action 
upon  light.  Placing  a  dark  surface  behind  the  beaker, 
and  permitting  the  light  to  fall  into  it  from  the  top  or 
front,  the  medium  is  seen  to  be  distinctly  blue.  It  is  not 
perhaps  so  perfect  a  blue  as  may  be  seen  on  exceptional 
days  among  the  Alps,  but  it  is  a  very  fair  sky-blue.  A 
trace  of  soap  in  water  gives  a  tint  of  blue.  London,  and 
I  fear  Liverpool,  milk  makes  an  approximation  to  the 
same  colour,  through  the  operation  of  the  same  cause  ; 
and  Helmholtz  has  irreverently  disclosed  the  fact  that 
the  deepest  blue  eye  is  simply  a  turbid  medium. 

The  action  of  turbid  media  upon  light  was  illustrated 
by  Goethe,  who,  though  unacquainted  with  the  undula- 
tory  theory,  was  led  by  his  experiments  to  regard  the 
firmament  as  an  illuminated  turbid  medium,  with  the  dark- 
ness of  space  behind  it.  He  describes  glasses  showing  a 
bright  yellow  by  transmitted,  and  a  beautiful  blue  by  re- 
flected, light.  Professor  Stokes,  who  was  probably  the 
first  to  discern  the  real  nature  of  the  action  of  small 


SCIENTIFIC   USE   OF   THE    IMAGINATION.  439 

particles  on  the  waves  of  aether,1  describes  a  glass  of  a 
similar  kind.2  Capital  specimens  of  such  glass  are  to  be 
found  at  Salviati's,  in  St.  James's  Street.  What  artists 
call  '  chill '  is  no  doubt  an  effect  of  this  description. 
Through  the  action  of  minute  particles,  the  browns  of  a 
picture  often  present  the  appearance  of  the  bloom  of  a 
plum.  By  rubbing  the  varnish  with  a  silk  handkerchief 
optical  continuity  is  established  and  the  chill  disappears. 
Some  years  ago  I  witnessed  Mr.  Hirst  experimenting  at 
Zermatt  on  the  turbid  water  of  the  Visp.  When  kept 
still  for  a  day  or  so,  the  grosser  matter  sank,  but  the 
finer  particles  remained  suspended,  and  gave  a  distinctly 
blue  tinge  to  the  water.  The  blueness  of  certain  Alpine 
lakes  has  been  shown  to  be  in  part  due  to  this  cause. 
Professor  Eoscoe  has  noticed  several  striking  cases  of  a 
similar  kind.  In  a  very  remarkable  paper  the  late 
Principal  Forbes  showed  that  steam  issuing  from  the 
safety-valve  of  a  locomotive,  when  favourably  observed, 
exhibits  at  a  certain  stage  of  its  condensation  the  colours 
of  the  sky.  It  is  blue  by  reflected  light,  and  orange  or 
red  by  transmitted  light.  The  same  effect  as  pointed  out 
by  Goethe,  is  to  some  extent  exhibited  by  peat-smoke. 
More  than  ten  years  ago  I  amused  myself  at  Killarney 
by  observing,  on  a  calm  day,  the  straight  smoke-columns 
rising  from  the  cabin  chimneys.  It  was  easy  to  project 
the  lower  portion  of  a  column  against  a  dark  pine,  and 
its  upper  portion  against  a  bright  cloud.  The  smoke  in 
the  former  case  was  blue,  being  seen  mainly  by  reflected 

1  This  is  inferred  from  conversation.     I  am  not  aware  that  Professor 
Stokes  has  published  anything  upon  the  subject. 

2  This  glass,  by  reflected  liglit,  had  a  colour  '  strongly  resembling  that 
of  a  decoction  of  horse-chestnut  bark.'     Curiously  enough  Goethe  refers  to 
this  very  decoction:  'Man  nehme  einen  Streifen  frischer  Rinde  von  der 
Kosskastanie,  man  stecke  denselben  in  ein  Glas  Wasser,  und  in  der  kiirzesten 
Zeit  \eerden  wir  das  vollkommenste  Himmelblau  entstehen  sehen.' — Goethe'a 
Werke,  b.  xxix.  p.  24. 


440  FKAGMENTS    OF   SCIENCE. 

light ;  in  the  latter  case  it  was  reddish,  being  seen  mainly 
by  transmitted  light.  Such  smoke  was  not  in  exactly  the 
condition  to  give  us  the  glow  of  the  Alps,  but  it  was  a 
step  in  this  direction.  Briicke's  fine  precipitate  above 
referred  to  looks  yellowish  by  transmitted  light ;  but,  by 
duly  strengthening  the  precipitate,  you  may  render  the 
white  light  of  noon  as  ruby-coloured  as  the  sun,  when 
seen  through  Liverpool  smoke,  or  upon  Alpine  horizons. 
I  do  not,  however,  point  to  the  gross  smoke  arising  from 
coal  as  an  illustration  of  the  action  of  small  particles, 
because  such  smoke  soon  absorbs  and  destroys  the  waves  of 
blue,  instead  of  sending  them  to  the  eyes  of  the  observer. 
These  multifarious  facts,  and  numberless  others  which 
cannot  now  be  referred  to,  are  explained  by  reference  to 
the  single  principle,  that,  where  the  scattering  particles 
are  small  in  comparison  to  the  aethereal  waves,  we  have 
in  the  reflected  light  a  greater  proportion  of  the  smaller 
waves,  and  in  the  transmitted  light  a  greater  proportion 
of  the  larger  waves,  than  existed  in  the  original  white  light. 
The  consequence,  as  regards  sensation,  is  that  in  the  one 
case  blue  is  predominant,  and  in  the  other  orange  or  red. 
Our  best  microscopes  can  readily  reveal  objects  not  more 
than  g-Q-J-o-oth  °f  an  incn  in  diameter.  This  is  less  than  the 
length  of  a  wave  of  red  light.  Indeed  a  first-rate  micro- 
scope would  enable  us  to  discern  objects  not  exceeding1  in 
diameter  the  length  of  the  smallest  waves  of  the  visible 
spectrum.  By  the  microscope,  therefore,  we  can  test  our 
particles.  If  they  be  as  large  as  the  light- waves  they  will 
infallibly  be  seen ;  and  if  they  be  not  so  seen,  it  is  because 
they  are  smaller.  I  placed  in  the  hands  of  our  President 
a  liquid  containing  Briicke's  precipitate.  The  liquid  was 
a  milky  blue,  and  Mr.  Huxley  applied  to  it  his  highest 
microscopic  power.  He  satisfied  me,  at  the  time,  that  had 
particles  of  even  1  0  J0  0  Oth  of  an  inch  in  diameter  existed 
in  the  liquid,  they  could  not  have  escaped  detection.  But 


SCIENTIFIC   USE   OF   THE   IMAGINATION.  441 

no  particles  were  seen.     Under  the  microscope  the  turbid 
liquid  was  not  to  be  distinguished  from  distilled  water.1 

But  we  have  it  in  our  power  to  imitate,  far  more  closely 
than  we  have  hitherto  done,  the  natural  conditions  of  this 
problem.  We  can  generate,  in  air,  artificial  skies,  and 
prove  their  perfect  identity  with  the  natural  one,  as 
regards  the  exhibition  of  a  number  of  wholly  unexpected 
phenomena.  By  a  continuous  process  of  growth,  moreover, 
we  are  able  to  connect  sky-matter,  if  I  may  use  the  term, 
with  molecular  matter  on  the  one  side,  and  with  molar 
matter,  or  matter  in  sensible  masses,  on  the  other.  In 
illustration  of  this  I  will  take  an  experiment  suggested 
by  some  of  my  own  researches,  and  described  by  M. 
Morren  of  Marseilles  at  the  Exeter  meeting  of  the 
British  Association.  Sulphur  and  oxygen  combine  to 
form  sulphurous  acid  gas,  two  atoms  of  oxygen  and 
one  of  sulphur  constituting  the  molecule  of  sulphurous 
acid.  It  has  been  recently  shown  that  waves  of 
aether  issuing  from  a  strong  source,  such  as  the  sun 
or  the  electric  light,  are  competent  to  shake  asunder 
the  atoms  of  gaseous  molecules.  A  chemist  would  call 
this,  '  decomposition '  by  light ;  but  it  behoves  us,  who  are 
examining  the  power  and  function  of  the  imagination,  to 
keep  constantly  before  us  the  physical  images  which 
underlie  our  terms.  Therefore  I  say,  sharply  and  defi- 
nitely, that  the  components  of  the  molecules  of  sul- 
phurous acid  are  shaken  asunder  by  the  aether-waves. 
Enclosing  sulphurous  acid  in  a  suitable  vessel,  placing  it 
in  a  dark  room,  and  sending  through  it  a  powerful  beam 
of  light,  we  at  first  see  nothing :  the  vessel  containing  the 
gas  seems  as  empty  as  a  vacuum.  Soon,  however,  along 

1  Like  Dr.  Burdon  Sanderson's  '  pyrogen,'  the  particles  of  mastic  passed, 
without  sensible  hindrance,  through  filtering-paper.  By  such  filtering  no 
freedom  from  suspended  particles  is  secured.  The  application  of  a  con- 
densed beam  to  the  filtrate  renders  this  at  once  evident.  1875. 


442  FRAGMENTS    OF   SCIENCE. 

the  track  of  the  beam  a  beautiful  sky-blue  colour  is  ob- 
served, which  is  due  to  light  scattered  by  the  liberated 
particles  of  sulphur.  For  a  time  the  blue  grows  more 
intense  ;  it  then  becomes  whitish  ;  and  ends  in  a  more  or 
less  perfect  white.  When  the  action  is  continued  long 
enough,  the  tube  is  filled  with  a  dense  cloud  of  sulphur 
particles,  which  by  the  application  of  proper  means  may 
be  rendered  individually  visible.1 

Here,  then,  our  aether-waves  untie  the  bond  of  chemical 
affinity,  and  liberate  a  body — sulphur — which  at  ordinary 
temperatures  is  a  solid,  and  which  therefore  soon  becomes 
an  object  of  the  senses.  We  have  first  of  all  the  free 
atoms  of  sulphur,  which  are  incompetent  to  stir  the  retina 
sensibly  with  scattered  light.  But  these  atoms  gradually 
coalesce  and  form  particles,  which  grow  larger  by  continual 
accretion,  until  after  a  minute  or  two  they  appear  as  sky- 
matter.  In  this  condition  they  are  themselves  invisible ; 
but  they  send  an  amount  of  wave-motion  to  the 
retina,  sufficient  to  produce  the  firmamental  blue.  The 
particles  continue,  or  may  be  caused  to  continue,  in 
this  condition  for  a  considerable  time,  during  which  no 
microscope  can  cope  with  them.  But  they  grow  slowly 
larger,  and  pass  by  insensible  gradations  into  the  state 
of  cloud,  when  they  can  no  longer  elude  the  armed 
eye.  Thus,  without  solution  of  continuity,  we  start  with 
matter  in  the  molecule,  and  end  with  matter  in  the 
mass;  sky-matter  being  the  middle  term  of  the  series  of 
transformations. 

Instead  of  sulphurous  acid,  we  might  choose  a  dozen 
other  substances,  and  produce  the  same  effect  with  all  of 
them.  In  the  case  of  some — probably  in  the  case  of  all 
— it  is  possible  to  preserve  matter  in  the  firmamental  con- 

1  M.  Morren  was  mistaken  in  supposing  that  a  modicum  of  sulphurous 
icid,  in  the  drying  tul>es,  had  any  share  in  the  production  of  the  'actinic 
clouds  '  described  by  me. 


SCIENTIFIC   USE   OF   THE   IMAGINATION.  443 

dition  for  fifteen  or  twenty  minutes  under  the  continual 
operation  of  the  light.  During  these  fifteen  or  twenty 
minutes  the  particles  constantly  grow  larger,  without  ever 
exceeding  the  size  requisite  to  the  production  of  the 
celestial  blue.  Now  when  two  vessels  are  placed  before 
us,  each  containing  sky-matter,  it  is  possible  to  state 
with  great  distinctness  which  vessel  contains  the  largest 
particles.  The  eye  is  very  sensitive  to  differences  of 
.ight,  when,  as  in  our  experiments,  it  is  in  compara- 
tive darkness,  and  the  wave-motion  thrown  against  the 
retina  is  small.  The  larger  particles  declare  themselves 
by  the  greater  whiteness  of  their  scattered  light.  Call 
now  to  mind  the  observation,  or  effort  at  observation, 
made  by  our  President,  when  he  failed  to  distinguish  the 
particles  of  mastic  in  Briicke's  medium,  and  when  you  have 
done  this,  please  follow  me.  A  beam  of  light  was  per- 
mitted to  act  upon  a  certain  vapour.  In  two  minutes  the 
azure  appeared,  but  at  the  end  of  fifteen  minutes  it  had 
uot  ceased  to  be  azure.  After  fifteen  minutes,  for  example, 
its  colour,  and  some  other  phenomena,  pronounced  it  to 
be  a  blue  of  distinctly  smaller  particles  than  those  sought 
for  in  vain  by  Mr.  Huxley.  These  particles,  as  already 
stated,  must  have  been  less  than  Tcx/pooth  of  an 
inch  in  diameter.  And  now  I  want  you  to  consider 
the  following  question  :  Here  are  particles  which 
have  been  growing  continually  for  fifteen  minutes, 
and  at  the  end  of  that  time  are  demonstrably  smaller 
than  those  which  defied  the  microscope  of  Mr.  Huxley — 
What  must  have  been  the  size  of  these  particles  at  the 
beginning  of  their  growth  ?  What  notion  can  you  form 
of  the  magnitude  of  such  particles  ?  The  distances  of 
stellar  space  give  us  simply  a  bewildering  sense  of 
vastness,  without  leaving  any  distinct  impression  on 
the  mind ;  and  the  magnitudes  with  which  we  have  here 
to  do,  bewilder  us  equally  in  the  opposite  direction. 


444  FRAGMENTS    OF   SCIENCE. 

We  are  dealing  with  infinitesimals,  compared  with 
which  the  test  objects  of  the  microscope  are  literally 
immense. 

From  their  perviousness  to  stellar  light,  and  other 
considerations,  Sir  John  Herschel  drew  some  startling 
conclusions  regarding  the  density  and  weight  of  comets. 
You  know  that  these  extraordinary  and  mysterious  bodies 
sometimes  throw  out  tails  100,000,000  of  miles  in 
length,  and  50,000  miles  in  diameter.  The  diameter  of 
our  earth  is  8,000  miles.  Both  it  and  the  sky,  and  a 
good  portion  of  space  beyond  the  sky,  would  certainly  be 
included  in  a  sphere  10,000  miles  across.  Let  us  fill  a 
hollow  sphere  of  this  diameter  with  cometary  matter, 
and  make  it  our  unit  of  measure.  To  produce  a  comet's 
tail  of  the  size  just  mentioned,  about  300,000  such 
measures  would  have  to  be  emptied  into  space.  Now  sup- 
pose the  whole  of  this  stuff  to  be  swept  together,  and 
suitably  compressed,  what  do  you  suppose  its  volume 
would  be  ?  Sir  John  Herschel  would  probably  tell  you 
that  the  whole  mass  might  be  carted  away,  at  a  single 
effort,  by  one  of  your  dray-horses.  In  fact,  I  do  not  know 
that  he  would  require  more  than  a  small  fraction  of  a 
horse-power  to  remove  the  cometary  dust.  After  this, 
you  will  hardly  regard  as  monstrous  a  notion  I  have 
sometimes  entertainec1,  concerning  the  quantity  of  matter 
in  our  sky.  Suppose  a  shell  to  surround  the  earth  at  a 
distance  which  would  place  it  beyond  the  grosser  matter  that 
hangs  in  the  lowe^  regions  of  the  air — say  at  the  height  of 
the  Matterhorn  or  Mont  Blanc.  Outside  this  shell  we  should 
have  the  deep  bJue  firmament.  Let  the  atmospheric  space 
beyond  the  shell  be  swept  clean,  and  the  sky-matter 
properly  gathered  up.  What  would  be  its  probable 
amount  ?  I  have  sometimes  thought  that  a  lady's  port- 
manteau would  contain  it  all.  I  have  thought  that  even  a 
gentleman's  portmanteau — possibly  his  snuff-box — might 


SCIENTIFIC  USE  OF  THE  IMAGINATION.  445 

take  it  in.  And,  whether  the  actual  sky  be  capable  of  this 
amount  of  condensation  or  not,  I  entertain  no  doubt  that 
a  sky  quite  as  vast  as  ours,  and  as  good  in  appearance, 
could  be  formed  from  a  quantity  of  matter  which  might 
be  held  in  the  hollow  of  the  hand. 

Small  in  mass,  the  vastness  in  point  of  number  of 
the  particles  of  our  sky  may  be  inferred  from  the  con- 
tinuity of  its  light.  It  is  not  in  broken  patches,  nor  at 
scattered  points,  that  the  heavenly  azure  is  revealed.  To 
the  observer  on  the  summit  of  Mont  Blanc,  the  blue  is  as 
uniform  and  coherent  as  if  it  formed  the  surface  of  the 
most  close-grained  solid.  A  marble  dome  would  not  ex- 
hibit a  stricter  continuity.  And  Mr.  Glaisher  will  inform 
you,  that  if  our  hypothetical  shell  were  lifted  to  twice 
the  height  of  Mont  Blanc  above  the  earth's  surface,  we 
should  still  have  the  azure  overhead.  Everywhere 
through  the  atmosphere  those  sky-particles  are  strewn. 
They  fill  the  Alpine  valleys,  spreading  like  a  delicate 
gauze  in  front  of  the  slopes  of  pine.  They  sometimes  so 
swathe  the  peaks  with  light  as  to  abolish  their  definition. 
This  year  I  have  seen  the  Weisshorn  thus  dissolved  in 
opalescent  air.  By  proper  instruments  the  glare  thrown 
from  the  sky-particles  against  the  retina  may  be  quenched, 
and  then  the  mountain  which  it  obliterated  starts  into 
sudden  definition.  Its  extinction  in  front  of  a  dark 
mountain  resembles  exactly  the  withdrawal  of  a  veil.  It 
is  the  light,  then,  taking  possession  of  the  eye,  and  not 
the  particles  acting  as  opaque  bodies,  that  interferes 
with  the  definition.  By  day  this  light  quenches  the 
stars ;  even  by  moonlight  it  is  able  to  exclude  from  vision 
all  stars  between  the  fifth  and  the  eleventh  magnitude. 
It  may  be  likened  to  a  noise,  and  the  feebler  stellar 
radiance  to  a  whisper  drowned  by  the  noise. 

What  is  the  nature  of  the  particles  which  shed  this 
light  ?     The  celebrated  De  la  Kive   ascribes  the  haze  of 


446  FRAGMENTS    OP   SCIENCE. 

the  Alps  in  fine  weather  to  floating  organic  germs.  Now 
the  possible  existence  of  germs  in  such  profusion  has  been 
held  up  as  an  absurdity.  It  has  been  affirmed  that  they 
would  darken  the  air,  and  on  the  assumed  impossibility 
of  their  existence  in  the  requisite  numbers,  without  inva- 
sion of  the  solar  light,  an  apparently  powerful  argument  has 
been  based  by  believers  in  spontaneous  generation.  Similar 
arguments  have  been  used  by  the  opponents  of  the  germ 
theory  of  epidemic  disease,  who  have  triumphantly  chal- 
lenged an  appeal  to  the  microscope  and  the  chemist's  balance 
to  decide  the  question.  Such  arguments,  however,  are 
founded  on  a  defective  acquaintance  with  the  powers  and 
properties  of  matter.  Without  committing  myself  in  the 
least  to  De  la  Eive's  notion,  to  the  doctrine  of  spontaneous 
generation,  or  to  the  germ  theory  of  disease,  I  would  simply 
draw  attention  to  the  demonstrable  fact,  that,  in  the  atmo- 
sphere, we  have  particles  which  defy  both  the  microscope 
and  the  balance,  which  do  not  darken  the  air,  and  which 
exist,  nevertheless,  in  multitudes  sufficient  to  reduce  to 
insignificance  the  Israelitish  hyperbole  regarding  the  sands 
upon  the  sea-shore. 

The  varying  judgments  of  men  on  these  and  other 
questions  may  perhaps  be,  to  some  extent,  accounted  for 
by  that  doctrine  of  Relativity  which  plays  so  important  a 
part  in  philosophy.  This  doctrine  affirms  that  the  impres- 
sions made  upon  us  by  any  circumstance,  or  combination 
of  circumstances,  depend  upon  our  previous  state.  Two 
travellers  upon  the  same  height,  the  one  having  ascended 
to  it  from  the  plain,  the  other  having  descended  to  it  from 
a  higher  elevation,  will  be  differently  affected  by  the  scene 
around  them.  To  the  one  nature  is  expanding,  to  the 
other  it  is  contracting,  and  feelings  which  have  two 
such  different  antecedent  states  are  sure  to  differ.  In 
our  scientific  judgments  the  law  of  relativity  may  also 
play  an  important  part.  To  two  men,  one  educated  in 


SCIENTIFIC  USE   OF   THE   IMAGINATION.  447 

the  school  of  the  senses,  having  mainly  occupied  himself 
with  observation  ;  the  other  educated  in  the  school  of  ima- 
gination as  well,  and  exercised  in  the  conceptions  of  atoms 
and  molecules  to  which  we  have  so  frequently  referred,  a 
bit  of  matter,  pay  ^  0  *  0  Oth  of  an  inch  in  diameter,  will 
present  itself  differently.  The  one  descends  to  it  from 
his  molar  heights,  the  other  climbs  to  it  from  his  mole- 
cular low-lands.  To  the  one  it  appears  small,  to  the 
other  large.  So,  also,  as  regards  the  appreciation  of  the 
most  minute  forms  of  life  revealed  by  the  microscope.  To 
one  of  the  men  these  naturally  appear  conterminous  with 
the  ultimate  particles  of  matter ;  there  is  but  a  step 
from  the  atom  to  the  organism.  The  other  discerns 
numberless  organic  gradations  between  both.  Compared 
with  his  atoms,  the  smallest  vibrios  and  bacteria  of  the 
microscopic  field  are  as  behemoth  and  leviathan.  The 
law  of  relativity  may  to  some  extent  explain  the  different 
attitudes  of 'two  such  persons  with  regard  to  the  question  of 
spontaneous  generation.  An  amount  of  evidence  which 
satisfies  the  one  entirely  fails  to  satisfy  the  other ;  and 
while  to  the  one  the  last  bold  defence  and  startling  ex- 
pansion of  the  doctrine  by  Dr.  Bastian  will  appear  per- 
fectly conclusive,  to  the  other  it  will  present  itself  as 
imposing  a  profitless  labour  of  demolition  on  subsequent 
investigators. 

Let  me  say  here  that  many  of  our  physiological  observers 
appear  to  form  a  very  inadequate  estimate  of  the  distance 
which  separates  the  microscopic  from  the  molecular  limit, 
and  that,  as  a  consequence,  they  sometimes  employ  a 
phraseology  calculated  to  mislead.  When,  for  example, 
the  contents  of  a  cell  are  described  as  perfectly  homo- 
geneous, or  as  absolutely  structureless,  because  the 
microscope  fails  to  distinguish  any  structure  ;  or  when 
two  structures  are  pronounced  to  be  without  difference, 
because  the  microscope  can  discover  none,  then  I  think 


i48  FRAGMENTS    OF    SCIENCE. 

the  microscope  begins  to  play  a  mischievous  part.  A  little 
consideration  will  make  it  plain  that  the  microscope  can 
have  no  voice  in  the  question  of  germ  structure.  Distilled 
water  is  more  perfectly  homogeneous  than  any  possible 
organic  germ.  What  is  it  that  causes  the  liquid  to  cease 
contracting  at  39°  Fahr.,  and  to  expand  until  it  freezes  ? 
This  is  a  structural  process  of  which  the  microscope  can  take 
no  note,  nor  is  it  likely  to  do  so  by  any  conceivable  exten- 
sion of  its  powers.  Place  distilled  water  in  the  field  of  an 
electro-magnet,  and  bring  a  microscope  to  bear  upon  it. 
Will  any  change  be  observed  when  the  magnet  is  excited: 
Absolutely  none ;  and  still  profound  and  complex  changes 
have  occurred.  First  of  all,  the  particles  of  water  have 
been  rendered  diamagnetically  polar  ;  and  secondly,  in 
yirtue  of  the  structure  impressed  upon  it  by  the  magnetic 
whirl  of  its  molecules,  the  liquid  twists  a  ray  of  light  in 
a  fashion  perfectly  determinate  both  as  to  quantity  and 
direction. 

Have  the  diamond,  the  amethyst,  and  the  countless 
other  crystals  formed  in  the  laboratories  of  nature  and  of 
man  no  structure  ?  Assuredly  they  have  ;  but  what  can 
the  microscope  make  of  it  ?  Nothing.  It  cannot  be  too 
distinctly  borne  in  mind  that  between  the  microscopic 
limit,  and  the  true  molecular  limit,  there  is  room  for 
infinite  permutations  and  combinations.  It  is  in  this  re- 
gion that  the  poles  of  the  atoms  are  arranged,  that  tendency 
is  given  to  their  powers  ;  so  that  when  these  poles  and 
powers  have  free  action,  proper  stimulus,  and  a  suitable 
environment,  they  determine,  first  the  germ,  and  after- 
wards the  complete  organism.  This  first  marshalling  of 
the  atoms,  on  which  all  subsequent  action  depends,  baffles 
a  keener  power  than  that  of  the  microscope.  When  duly 
pondered,  the  complexity  of  the  problem  raises  the  doubt, 
not  of  the  power  of  our  instrument,  for  that  is  nil,  but 
whether  we  ourselves  possess  the  intellectual  elements 


SCIENTIFIC   USE    OF   THE    IMAGINATION.  119 

which  will  ever  enable  us  to  grapple  with  the  ultimate 
structural  energies  of  nature.1 

In  more  senses  than  one  Mr.  Darwin  has  drawn 
heavily  upon  the  scientific  tolerance  of  his  age.  He 
has  drawn  heavily  upon  time  in  his  development  of  species, 
and  he  has  drawn  adventurously  upon  matter  in  his  theory 
of  pangenesis.  According  to  this  theory,  a  germ  already 
microscopic  is  a  world  of  minor  germs.  Not  only  is  the 
organism  as  a  whole  wrapped  up  in  the  germ,  but  every 
organ  of  the  organism  has  there  its  special  seed.  This,  I 
say,  is  an  adventurous  draft  on  the  power  of  matter  to 
divide  itself  and  distribute  its  forces.  But,  unless  we  are 
perfectly  sure  that  he  is  overstepping  the  bounds  of  rea- 
son, that  he  is  unwittingly  sinning  against  observed  fact 
or  demonstrated  law — for  a  mind  like  that  of  Darwin  can 
never  sin  wittingly  against  either  fact  or  law — we  ought, 
I  think,  to  be  cautious  in  limiting  his  intellectual  hori- 
zon. If  there  be  the  least  doubt  in  the  matter,  it  ought 
to  be  given  in  favour  of  the  freedom  of  such  a  mind.  To 
it  a  vast  possibility  is  in  itself  a  dynamic  power,  though 
the  possibility  may  never  be  drawn  upon.  It  gives  me 
pleasure  to  think  that  the  facts  and  reasonings  of  this 
discourse  tend  rather  towards  the  justification  of  Mr. 
Darwin,  than  towards  his  condemnation ;  that  they  tend 
rather  to  augment  than  to  diminish  the  cubic  space  de- 
manded by  this  soaring  speculator.  For  they  seem  to 
show  the  perfect  competence  of  matter  and  force,  as  re- 

1  'In  using  the  expression  "one  sort  of  living  substance"  I  must  guard 
against  being  supposed  to  mean  that  any  kind  of  living  protoplasm  is 
homogeneous.  Hyaline  though  it  may  appear,  we  are  n^t  at  present  able 
to  assign  any  limit  to  its  complexity  of  structure. — Burdon  Sanderson,  in 
the  '  British  Medical  Journal,'  January  16,  1875. 

We  have  here  scientific  insight,  and  its  correlative  caution.  In  fact 
Dr.  Sanderson's  important  researches  are  a  continued  illustration  of  the  po- 
gition  laid  down  above. 


100  FKAGMENTS    OF   SCIENCE. 

gards  divisibility  and  distribution,  to  bear  the  heaviest 
strain  that  he  has  hitherto  imposed  upon  them. 

In  the  case  of  Mr.  Darwin,  observation,  imagination, 
and  reason  combined,  have  run  back  with  wonderful 
sagacity  and  success  over  a  certain  length  of  the  line  of 
biological  succession.  Guided  by  analogy,  in  his  '  Origin 
of  Species '  he  placed  at  the  root  of  life  a  primordial 
germ,  from  which  he  conceived  the  amazing  richness  and 
variety  of  the  organisms  now  upon  the  earth's  surface 
might  be  deduced.  If  this  hypothesis  were  even  true,  it 
would  not  be  final.  The  human  mind  would  in- 
fallibly look  behind  the  germ,  and,  however  hopeless  the 
attempt,  would  enquire  into  the  history  of  its  genesis.  In 
this  dim  twilight  of  conjecture  the  searcher  welcomes 
every  gleam,  and  seeks  to  augment  his  light  by  indirect 
incidences.  He  studies  the  methods  of  nature  in  the  ages 
and  the  worlds  within  his  reach,  in  order  to  shape  the  course 
of  speculation  in  the  antecedent  ages  and  worlds.  And 
though  the  certainty  possessed  by  experimental  enquiry  is 
here  shut  out,  we  are  not  left  entirely  without  guidance. 
From  the  examination  of  the  solar  system,  Kant  and 
Laplace  came  to  the  conclusion  that  its  various  bodies 
once  formed  parts  of  the  same  undislocated  mass  ;  that 
matter  in  a  nebulous  form  preceded  matter  in  its  present 
form  ;  that  as  the  ages  rolled  away,  heat  was  wasted, 
condensation  followed,  planets  were  detached ;  and  that 
finally  the  chief  portion  of  the  hot  cloud  reached,  by 
self-compression,  the  magnitude  and  density  of  our  sun. 
The  earth  itself  offers  evidence  of  a  fiery  origin  ;  and  in 
our  day  the  hypothesis  of  Kant  and  Laplace  receives  the 
independent  countenance  of  spectrum  analysis,  which 
proves  the  same  substances  to  be  common  to  the  earth 
and  sun. 

Accepting  some  such  view  of  the  construction  of  our 


SCIENTIFIC   USE   OF   THE   IMAGINATION.  451 

system  as  probable,  a  desire  immediately  arises  to  connect 
the  present  life  of  our  planet  with  the  past.  We  wish  to 
know  something  of  our  remotest  ancestry.  On  its  first 
detachment  from  the  central  mass,  life,  as  we  understand 
it,  could  not  have  been  present  on  the  earth.  How,  then, 
did  it  come  there  ?  The  thing  to  be  encouraged  here  is  a 
reverent  freedom — a  freedom  preceded  by  the  hard  dis- 
cipline which  checks  licentiousness  in  speculation — while 
the  thing  to  be  repressed,  both  in  science  and  out  of  it,  is 
dogmatism.  And  here  I  am  in  the  hands  of  the  meeting 
— willing  to  end,  but  ready  to  go  on.  I  have  no  right  to 
intrude  upon  you,  unasked,  the  unformed  notions  which 
are  floating  like  clouds,  or  gathering  to  more  solid  con- 
sistency, ill  the  modern  speculative  scientific  mind.  But 
if  you  wish  me  to  speak  plainly,  honestly,  and  undispu- 
tatiously,  I  am  willing  to  do  so.  On  the  present  occa- 
sion— 

You  are  ordained  to  call,  and  I  to  come. 

Well,  your  answer  is  given,  and  I  obey  your  call. 

Two  or  three  years  ago,  in  an  ancient  London 
College,  I  listened  to  a  discussion  at  the  end  of  a 
lecture  by  a  very  remarkable  man.  Three  or  four 
hundred  clergymen  were  present  at  the  lecture.  The 
orator  began  with  the  civilisation  of  Egypt  in  the 
time  of  Joseph ;  pointing  out  the  very  perfect  organi- 
sation of  the  kingdom,  and  the  possession  of  chariots, 
in  one  of  which  Joseph  rode,  as  proving  a  long  antecedent 
period  of  civilisation.  He  then  passed  on  to  the  mud  of 
the  Nile,  its  rate  of  augmentation,  its  present  thickness, 
and  the  remains  of  human  handiwork  found  therein ; 
thence  to  the  rocks  which  bound  the  Nile  valley,  and 
which  teem  with  organic  remains.  Thus  in  his  own  clear 
and  admirable  way  he  caused  the  idea  of  the  world's  age 
to  expand  itself  indefinitely  before  the  minds  of  his  audi- 
ence, and  he  contrasted  this  with  the  age  usually  assigned 


452  FRAGMENTS    OF   SCIENCE. 

to  the  world.  During  his  discourse  he  seemed  to  "be 
swimming  against  a  stream ;  he  manifestly  thought  that 
he  was  opposing  a  general  conviction.  He  expected 
resistance  ;  so  did  I.  But  it  was  all  a  mistake :  there 
was  no  adverse  current,  no  opposing  conviction,  no  resist- 
ance; merely  here  and  there  a  half-humorous,  but  un- 
successful, attempt  to  entangle  him  in  his  talk.  The 
meeting  agreed  with  all  that  had  been  said  regarding  the 
antiquity  of  the  earth  and  of  its  life.  They  had,  indeed, 
known  it  all  long  ago,  and  they  rallied  the  lecturer  for 
coming  amongst  them  with  so  stale  a  story.  It  was 
quite  plain  that  this  large  body  of  clergymen,  who  were, 
I  should  say,  the  finest  samples  of  their  class,  had  en- 
tirely given  up  the  ancient  landmarks,  and  transported 
the  conception  of  life's  origin  to  an  indefinitely  distant 
past. 

This  leads  us  to  the  gist  of  our  present  enquiry,  which 
is  this :  Does  life  belong  to  what  we  call  matter,  or  is 
it  an  independent  principle  inserted  into  matter  at  some 
suitable  epoch — say,  when  the  physical  conditions  became 
such  as  to  permit  of  the  development  of  life  ?  Let  us 
put  the  question  with  the  reverence  due  to  a  faith 
and  culture  in  which  we  all  were  cradled,  and  which 
are  the  undeniable  historic  antecedents  of  our  present 
enlightenment.  I  say,  let  us  put  the  question  reverently, 
but  let  us  also  put  it  clearly  and  definitely.  There  are 
the  strongest  grounds  for  believing  that  during  a  certain 
period  of  its  history  the  earth  was  not,  nor  was  it  fit 
to  be,  the  theatre  of  life.  Whether  this  was  ever  a 
nebulous  period,  or  merely  a  molten  period,  does  not 
much  matter ;  and  if  we  revert  to  the  nebulous  condition, 
it  is  because  the  probabilities  are  really  on  its  side.  Our 
question  is  this  :  Did.  creative  energy  pause  until  the 
nebulous  matter  had  condensed,  until  the  earth  had  been 
detached,  until  the  solar  fire  had  so  far  withdrawn  from 


SCIENTIFIC  USE   OF   THE   IMAGINATION.  453 

the  earth's  vicinity  as  to  permit  a  crust  to  gather  round 
the  planet  ?  Did  it  wait  until  the  air  was  isolated  ;  until 
the  seas  were  formed;  until  evaporation,  condensation,  and 
the  descent  of  rain  had  begun ;  until  the  eroding  forces 
of  the  atmosphere  had  weathered  and  decomposed  the 
molten  rocks  so  as  to  form  soils ;  until  the  sun's  rays  had 
become  so  tempered  by  distance,  and  by  waste,  as  to  be 
chemically  fit  for  the  decompositions  necessary  to  vege- 
table life  ?  Having  waited  through  those  aeons  until  the 
proper  conditions  had  set  in,  did  it  send  the  fiat  forth, 
'  Let  there  be  Life  I '  ?  These  questions  define  a  hypo- 
thesis not  without  its  difficulties,  but  the  dignity  of  which 
was  demonstrated  by  the  nobleness  of  the  men  whom  it 
sustained. 

Modern  scientific  thought  is  called  upon  to  decide 
between  this  hypothesis  and  another  ;  and  public  thought 
generally  will  afterwards  be  called  upon  to  do  the  same. 
But,  however  the  convictions  of  individuals  here  and 
there  may  be  influenced,  the  process  must  be  slow  and 
secular  which  commends  the  hypothesis  of  Natural  Evolu- 
tion to  the  public  mind.  For  what  are  the  core  and 
essence  of  this  hypothesis  ?  Strip  it  naked,  and  you 
stand  face  to  face  with  the  notion  that  not  alone  the 
more  ignoble  forms  of  animalcular  or  animal  life,  not 
alone  the  nobler  forms  of  the  horse  and  lion,  not  alone 
the  exquisite  and  wonderful  mechanism  of  the  human 
body,  but  that  the  human  mind  itself — emotion,  intellect, 
will,  and  all  their  phenomena — were  once  latent  in  a  fiery 
cloud.  Surely  the  mere  statement  of  such  a  notion  is 
more  than  a  refutation.  But  the  hypothesis  would  pro- 
bably go  even  farther  than  this.  Many  who  hold  it 
would  probably  assent  to  the  position  that,  at  the  present 
moment,  all  our  philosophy,  all  our  poetry,  all  our  science, 
and  all  our  art — Plato,  Shakspeare,  Newton,  and  Eaphael 
— are  potential  in  the  fires  of  the  sun.  We  long  to  learn 


i54  FRAGMENTS    OF   SCIENCE. 

something  of  our  origin.  If  the  Evolution  hypothesis  be 
correct,  even  this  unsatisfied  yearning  must  have  come  to 
us  across  the  ages  which  separate  the  unconscious  primeval 
mist  from  the  consciousness  of  to-day.  I  do  not  think 
that  any  holder  of  the  Evolution  hypothesis  would  say 
that  I  overstate  or  overstrain  it  in  any  way.  I  merely 
strip  it  of  all  vagueness,  and  bring  before  you,  unclothed 
and  unvarnished,  the  notions  by  which  it  must  stand  or 
fall. 

Surely  these  notions  represent  an  absurdity  too  mon- 
strous to  be  entertained  by  any  sane  mind.  But  why  are 
such  notions  absurd,  and  why  should  sanity  reject  them  ? 
The  law  of  Relativity,  of  which  we  have  previously  spoken, 
may  find  its  application  here.  These  Evolution  notions 
are  absurd,  monstrous,  and  fit  only  for  the  intellectual 
gibbet,  in  relation  to  the  ideas  concerning  matter  which 
were  drilled  into  us  when  young.  Spirit  and  matter  have 
ever  been  presented  to  us  in  the  rudest  contrast,  the  one 
as  all-noble,  the  other  as  all-vile.  But  is  this  correct  ? 
Upon  the  answer  to  this  question  all  depends.  Supposing 
that,  instead  of  having  the  foregoing  antithesis  of  spirit 
and  matter  presented  to  our  youthful  minds,  we  had 
been  taught  to  regard  them  as  equally  worthy,  and 
equally  wonderful ;  to  consider  them,  in  fact,  as  two  op- 
posite faces  of  the  self-same  mystery.  Supposing  that  in 
youth  we  had  been  impregnated  with  the  notion  of  the  poet 
Goethe,  instead  of  the  notion  of  the  poet  Young,  looking 
at  matter,  not  as  brute  matter,  but  as  the  '  living  garment 
of  God  ; '  do  you  not  think  that  under  these  altered  cir- 
cumstances the  law  of  Relativity  might  have  had  an 
outcome  different  from  its  present  one  ?  Is  it  not  pro- 
bable that  our  repugnance  to  the  idea  of  primeval  union 
between  spirit  and  matter  might  be  considerably  abated  ? 
Without  this  total  revolution  of  the  notions  now  pre- 
Falent,  the  Evolution  hypothesis  must  stand  condemned ; 


SCIENTIFIC   USE   OF   THE   IMAGINATION.  455 

but  in  many  profoundly  thoughtful  minds  such  a  revolu- 
tion has  already  taken  place.  They  degrade  neither 
member  of  the  mysterious  duality  referred  to  ;  but  they 
exalt  one  of  them  from  its  abasement,  and  repeal  the 
divorce  hitherto  existing  between  both.  In  substance,  if 
not  in  words,  their  position  as  regards  the  relation  of 
spirit  and  matter  is  :  '  What  God  hath  joined  together  let 
not  man  put  asunder.' 

You  have  been  thus  led  to  the  outer  rim  of  speculative 
science,  for  beyond  the  nebulae  scientific  thought  has 
never  hitherto  ventured.  I  have  tried  to  state  that  which 
I  considered  ought,  in  fairness,  to  be  outspoken.  I 
neither  think  this  Evolution  hypothesis  is  to  be  flouted 
away  contemptuously,  nor  that  it  ought  to  be  denounced 
as  wicked.  It  is  to  be  brought  before  the  bar  of  dis- 
ciplined reason,  and  there  justified  or  condemned.  Let 
us  hearken  to  those  who  wisely  support  it,  and  to  those 
who  wisely  oppose  it ;  and  let  us  tolerate  those,  whose 
name  is  legion,  who  try  foolishly  to  do  either  of  these 
things.  The  only  thing  out  of  place  in  the  discussion  is 
dogmatism  on  either  side.  Fear  not  the  Evolution  hypo- 
thesis. Steady  yourselves,  in  its  presence,  upon  that  faith 
in  the  ultimate  triumph  of  truth  which  was  expressed 
by  old  Gamaliel  when  he  said:  'If  it  be  of  God,  ye 
cannot  overthrow  it ;  if  it  be  of  man,  it  will  come  to 
nought.'  Under  the  fierce  light  of  scientific  enquiry, 
it  is  sure  to  be  dissipated  if  it  possess  not  a  core  of  truth. 
Trust  me,  its  existence  as  a  hypothesis  is  quite  com- 
patible with  the  simultaneous  existence  of  all  those  virtues 
to  which  the  term  '  Christian '  has  been  applied.  It  does 
not  solve — it  does  not  profess  to  solve — the  ultimate 
mystery  of  this  universe.  It  leaves,  in  fact,  that  mystery 
untouched.  For,  granting  the  nebula  and  its  potential 
life,  the  question,  whence  they  came,  would  still  remain 
to  baffle  and  bewilder  us.  At  bottom,  the  hypothesis  does 


150  FRAGMENTS   OF   SCIENCE. 

nothing  more  than  '  transport  the  conception  of  life's  origin 
to  an  indefinitely  distant  past.' 

Those  who  hold  the  doctrine  of  Evolution  are  by  no 
means  ignorant  of  the  uncertainty  of  their  data,  and  they 
only  yield  to  it  a  provisional  assent.  They  regard  the 
nebular  hypothesis  as  probable,  and,  in  the  utter  absence 
of  any  evidence  to  prove  the  act  illegal,  they  extend  the 
method  of  nature  from  the  present  into  the  past.  Here 
the  observed  uniformity  of  nature  is  their  only  guide. 
"Within  the  long  range  of  physical  enquiry,  they  have 
never  discerned  in  nature  the  insertion  of  caprice. 
Throughout  this  range,  the  laws  of  physical  and  intel- 
lectual continuity  have  run  side  by  side.  Having  thus 
determined  the  elements  of  their  curve  in  a  world  of 
observation  and  experiment,  they  prolong  that  curve  into 
an  antecedent  world,1  and  accept  as  probable  the  unbroken 
sequence  of  development  from  the  nebula  to  the  present 
time.  You  never  hear  the  really  philosophical  defenders 
of  the  doctrine  of  Uniformity  speaking  of  impossibilities 
in  nature.  They  never  say,  what  they  are  constantly 
charged  w'th  saying,  that  it  is  impossible  for  the  Builder 
of  the  universe  to  alter  His  work.  Their  business  is 
not  with  the  possible,  but  the  actual — not  with  a  world 
which  might  be,  but  with  a  world  that  is.  This  they 
explore  with  a  courage  not  unmixed  with  reverence,  and 
according  to  methods  which,  like  the  quality  of  a  tree,  are 
tested  by  their  fruits.  They  have  but  one  desire — to 
know  the  truth.  They  have  but  one  fear — to  believe  a 
lie.  And  if  they  know  the  strength  of  science,  and  rely 
upon  it  with  unswerving  trust,  they  also  know  the  limits 
beyond  which  science  ceases  to  be  strong.  They  best  know 
that  questions  offer  themselves  to  thought,  which  science, 
as  now  prosecuted,  has  not  even  the  tendency  to  solve. 

1  See  '  Belfast  Address,'  p.  507  ;  and  '  Apology,'  p.  544. 


ON   THE  MATTERHORN.  457 

They  keep  such  questions  open,  and  will  not  tolerate  any 
unnecessary  limitation  of  the  horizon  of  their  souls.  They 
have  as  little  fellowship  with  the  atheist  who  says  there  is 
no  God,  as  with  the  theist  who  professes  to  know  the  mind 
of  Gk>d.  '  Two  things,'  said  Immanuel  Kant,  'fill  me  with 
awe  :  the  starry  heavens,  and  the  sense  of  moral  responsi- 
bility in  man.'  And  in  his  hours  of  health  and  strength 
and  sanity,  when  the  stroke  of  action  has  ceased,  and  the 
pause  of  reflection  has  set  in,  the  scientific  investigator 
finds  himself  overshadowed  by  the  same  awe.  Breaking 
contact  with  the  hampering  details  of  earth,  it  associates 
him  with  a  Power  which  gives  fulness  and  tone  to  his 
existence,  but  which  he  can  neither  analyse  nor  com- 
prehend. 


Musings  on  the  Matterhorn,  July  27,  1868. 

'  Hacked  and  hurt  bv  time,  the  aspect  of  the  moun- 
tain from  its  higher  crags  saddened  me.  Hitherto  the 
impression  it  made  was  that  of  savage  strength  ;  here  we 
had  inexorable  decay.  But  this  notion  of  decay  implied 
a  reference  to  a  period  when  the  Matterhorn  was  in  the 
full  strength  of  mountainhood.  Thought  naturally  ran 
back  to  its  remoter  origin  and  sculpture.  Nor  did 
thought  halt  there,  but  wandered  on  through  molten 
worlds  to  that  nebulous  haze  which  philosophers  have  re- 
garded, and  with  good  reason,  as  the  proximate  source  of 
all  material  things.  I  tried  to  look  at  this  universal 
cloud,  containing  within  itself  the  prediction  of  all  that 
has  since  occurred  ;  I  tried  to  imagine  it  as  the  seat  of 
those  forces  whose  action  was  to  issue  in  solar  and  stellar 
systems,  and  all  that  they  involve.  Did  that  formless  fog 
contain  potentially  the  sadness  with  which  I  regarded 


458  FRAGMENTS    OF   SCIENCE. 

the  Matterhorn  ?  Did  the  thought  which  now  ran  back 
to  it  simply  return  to  its  primeval  home  ?  If  so,  had  we 
not  brtter  recast  our  definitions  of  matter  and  force ;  for,  if 
life  and  thought  be  the  very  flower  of  both,  any  definition 
which  omits  life  and  thought  must  be  inadequate,  if  not 
untrue.  Are  questions  like  these  warranted  ?  Why  not  ? 
If  the  final  goal  of  man  has  not  been  yet  attained  ;  if  his 
development  has  not  been  yet  arrested,  who  can  say  that 
such  yearnings  and  questionings  are  not  necessary  to  the 
opening  of  a  finer  vision,  to  the  budding  and  the  growth 
of  diviner  powers?  When  I  look  at  the  heavens  and  the 
earth,  at  my  own  body,  at  my  strength  and  weakness, 
even  at  these  ponderings,  and  ask  myself,  Is  there  no 
being  or  thing  in  the  universe  that  knows  more  about 
these  matters  than  I  do  ;  what  is  my  answer  ?  !  Supposing 
our  theologic  schemes  of  creation,  condemnation,  and 
redemption  to  be  dissipated ;  and  the  warmth  of  denial 
which  they  excite,  and  which,  as  a  motive  force,  can  match 
the  warmth  of  affirmation,  dissipated  at  the  same  time ; 
would  the  undeflected  human  mind  return  to  the  meridian 
of  absolute  neutrality  as  regards  these  ultra-physical 
questions  ?  Is  such  a  position  one  of  stable  equilibrium  ? 
The  channels  of  thought  being  already  formed,  such  are 
the  questions,  without  replies,  which  could  run  athwart 
consciousness  during  a  ten  minutes'  halt  upon  the 
weathered  crest  of  the  Matterhorn.' 

1  See  p.  407. 


V. 

VITALITY. 
1865. 


fHHE  origin,  growth,  and  energies  of  living  things  are 
-L  subjects  which  have  always  engaged  the  attention  of 
thinking  men.  To  account  for  them  it  was  usual  to  assume 
a  special  agent,  free  to  a  great  extent  from  the  limitations 
observed  among  the  powers  of  inorganic  nature.  This  agent 
was  called  the  vital  force  ;  and,  under  its  influence,  plants 
and  animals  were  supposed  to  collect  their  materials  and 
to  assume  determinate  forms.  Within  the  last  few  years, 
however,  our  ideas  of  vital  processes  have  undergone  pro- 
found modifications;  and  the  interest,  and  even  disquietude, 
which  the  change  has  excited  are  amply  evidenced  by  the 
discussions  and  protests  which  are  now  common  regarding 
the  phenomena  of  vitality.  In  tracing  these  phenomena, 
through  all  their  modifications,  the  most  advanced  philoso- 
phers of  the  present  day  declare  that  they  ultimately  arrive 
at  a  single  source  of  power,  from  which  all  vital  energy  is 
derived  ;  and  the  disquieting  circumstance  is  that  this 
source  is  not  the  direct  fiat  of  a  supernatural  agent,  but  a 
reservoir  of  what,  if  we  do  not  accept  the  creed  of  Zoroaster, 
must  be  regarded  as  inorganic  force.  In  short,  it  is  con- 
sidered as  proved  that  all  the  energy  which  we  derive  from 
plants  and  animals  is  drawn  from  the  sun. 

A  few  years  ago,  when  the  sun  was  affirmed  to  be  the 
source  of  life,  nine  out  of  ten  of  those  who  are  alarmed  by 
the  form  which  this  assertion  has  latterly  assumed  would 
22 


460  FKAGMENTS   OF  SCIENCE. 

have  assented,  in  a  general  way,  to  its  correctness.  Their 
assent,  however,  was  more  poetic  than  scientific,  and  they 
were  by  no  means  prepared  to  see  a  rigid  mechanical  sig- 
nification attached  to  their  words.  This,  however,  is  the 
peculiarity  of  modern  conclusions : — that  there  is  no  creative 
energy  whatever  in  the  vegetable  or  animal  organism,  but 
that  all  the  power  which  we  obtain  from  the  muscles  of 
man  and  animals,  as  much  as  that  which  we  develop  by 
the  combustion  of  wood  or  coal,  has  been  produced  at  the 
sun's  expense.  The  sun  is  so  much  colder  that  we  may  have 
our  fires  ;  he  is  also  so  much  colder  that  we  may  have  our 
horse-racing  and  Alpine  climbing.  It  is,  for  example, 
certain  that  the  sun  has  been  chilled  to  an  extent  capable 
of  being  accurately  expressed  in  numbers,  in  order  to  fur- 
nish the  power  which  lifted  this  year  a  certain  number  of 
tourists  from  the  vale  of  Chamouni  to-  the  summit  of  Mont 
Blanc. 

To  most  minds,  however,  the  energy  of  light  and  heat 
presents  itself  as  a  thing  totally  distinct  from  ordinary  me- 
chanical energy.  But  either  of  them  can  be  derived  from 
the  other.  Wood  can  be  raised  by  friction  to  the  tempera- 
ture of  ignition  ;  while  by  properly  striking  a  piece  of  iron 
a  skilful  blacksmith  can  cause  it  to  glow.  Thus,  by  the 
rude  agency  of  his  hammer,  he  generates  light  and  heat. 
This  action,  if  carried  far  enough,  would  produce  the  light 
and  heat  of  the  sun.  In  fact  the  sun's  light  and  heat  have 
actually  been  referred  to  the  fall  of  meteoric  matter  upon 
his  surface ;  and  whether  the  sun  is  thus  supported  or  not, 
it  is  perfectly  certain  that  he  might  be  thus  supported. 
Whether,  moreover,  the  whilom  molten  condition  of  our 
planet  was,  as  supposed  by  eminent  men,  due  to  the  collision 
of  cosmic  masses  or  not,  it  is  perfectly  certain  that  the 
molten  condition  might  be  thus  brought  about.  If,  then, 
solar  light  and  heat  can  be  produced  by  the  impact  of  dead 
matter,  and  if  from  the  light  and  heat  thus  produced  we  can 


VITALITY.  461 

derive  the  energies  which  we  have  been  accustomed  to  call 
vital,  it  indubitably  follows  that  vital  energy  may  have  a 
proximately  mechanical  origin. 

In  what  sense,  then,  is  the  sun  to  be  regarded  as  the 
origin  of  the  energy  derivable  from  plants  and  animals  ? 
Let  us  try  to  give  an  intelligible  answer  to  this  question. 
Water  may  be  raised  from  the  sea-level  to  a  high  elevation, 
and  then  permitted  to  descend.  In  descending  it  may  be 
made  to  assume  various  forms — to  fall  in  cascades,  to  spurt 
in  fountains,  to  boil  in  eddies,  or  to  flow  tranquilly  along  a 
uniform  bed.  It  may,  moreover,  be  caused  to  set  complex 
machinery  in  motion,  to  turn  millstones,  throw  shuttles, 
work  saws  and  hammers,  and  drive  piles.  But  every  form 
of  power  here  indicated  would  be  derived  from  the  original 
power  expended  in  raising  the  water  to  the  height  from 
which  it  fell.  There  is  no  energy  generated  by  the 
machinery  ;  the  work  performed  by  the  water  in  de- 
scending is  merely  the  parcelling  out  and  distribution  of 
the  work  expended  in  raising  it.  In  precisely  this  sense 
is  all  the  energy  of  plants  and  animals  the  parcelling  out 
and  distribution  of  a  power  originally  exerted  by  the  sun. 
In  the  case  of  the  water,  the  source  of  the  power  consists  in 
the  forcible  separation  of  a  quantity  of  the  liquid  from 
a  low  level  of  the  earth's  surface,  and  its  elevation  to  a 
higher  position,  the  power  thus  expended  being  returned 
by  the  water  in  its  descent.  In  the  case  of  vital  pheno- 
mena, the  source  of  power  consists  in  the  forcible  separa- 
tion of  the  atoms  of  compound  substances  by  the  sun.1  We 
name  the  force  which  draws  the  water  earthward  *  gravity,' 
and  that  which  draws  atoms  together  'chemical  affinity ; ' 
but  these  different  names  must  not  mislead  us  regarding 
the  qualitative  identity  of  the  two  forces.  They  are 
both  attractions ;  and,  to  the  intellect,  the  falling  of  carbon 

1  Referred  to  further  in  Arts.  I.,  III.,  and  IV.,  Parti.  •  and  Art.  VIII., 
Part  II. 


462  FRAGMENTS   OF  SCIENCE. 

atoms  against  oxygen  atoms  is  not  more  difficult  of  con- 
ception than  the  falling  of  water  to  the  earth. 

The  building  up  01  the  vegetable,  then,  is  effected  by 
the  sun,  through  the  reduction  of  chemical  compounds. 
The  phenomena  of  animal  life  are  more  or  less  complicated 
reversals  of  these  processes  of  reduction.  We  eat  the 
vegetable,  and  we  breathe  the  oxygen  of  the  air;  and  in  our 
bodies  the  oxygen,  which  had  been  lifted  from  the  carbon 
and  hydrogen  by  the  action  of  the  sun,  again  falls  towards 
them,  producing  animal  heat  and  developing  animal  forms. 
Through  the  most  complicated  phenomena  of  vitality  this 
law  runs  : — the  vegetable  is  produced  while  a  weight  rises, 
the  animal  is  produced  while  a  weight  falls.  But  the  ques- 
tion is  not  exhausted  here.  The  water  employed  in  our 
first  illustration  generates  all  the  motion  displayed  in  its 
descent,  but  the  form  of  the  motion  depends  on  the  cha- 
racter of  the  machinery  interposed  in  the  path  of  the 
water.  In  a  similar  way,  the  primary  action  of  the  sun's 
rays  is  qualified  by  the  atoms  and  molecules  among  which 
their  energy  is  distributed.  Molecular  forces  determine 
the  form  which  the  solar  energy  will  assume.  In  the  sepa- 
ration of  the  carbon  and  oxygen  this  energy  may  be  so  con- 
ditioned as  to  result  in  one  case  in  the  formation  of  a 
cabbage,  and  in  another  case  in  the  formation  of  an  oak. 
So  also,  as  regards  the  reunion  of  the  carbon  and  the  oxygen, 
the  molecular  machinery  through  which  the  combining 
energy  acts  may,  in  one  case,  weave  the  texture  of  a  frog 
while  in  another  it  may  weave  the  texture  of  a  man. 

The  matter  of  the  animal  body  is  that  of  inorganic 
nature.  There  is  no  substance  in  the  animal  tissues  which 
is  not  primarily  derived  from  the  rocks,  the  water,  and 
the  air.  Are  the  forces  of  organic  matter,  then,  different 
in  kind  from  those  of  inorganic  matter  ?  The  philosophy 
of  the  present  day  negatives  the  question.  It  is  the 
compounding,  in  the  organic  world,  of  forces  belonging 


VITALITY.  4G3 

equally  to  the  inorganic,  that  constitutes  the  mystery  and 
the  miracle  of  vitality.  Every  portion  of  every  animal  body 
may  be  reduced  to  purely  inorganic  matter.  A  perfect  re- 
versal of  this  process  of  reduction  would  carry  us  from  the 
inorganic  to  the  organic ;  and  such  a  reversal  is  at  least 
conceivable.  The  tendency,  indeed,  of  modern  science  is 
to  break  down  the  wall  of  partition  between  organic  and 
inorganic,  and  to  reduce  both  to  the  operation  of  forces 
which  are  the  same  in  kind,  but  which  are  variously  com- 
pounded. 

Consider  the  question  of  personal  identity,  in  relation 
to  that  of  molecular  form.  Twenty-six  years  ago  Mayer, 
of  Heilbronn,  with  that  power  of  genius  which  breathes 
large  meanings  into  scanty  facts,  pointed  out  that  the  blood 
was  '  the  oil  of  the  lamp  of  life,'  the  combustion  of  which, 
like  that  of  coal  in  grosser  cases,  sustains  muscular  action. 
The  muscles  are  the  machinery  by  which  the  dynamic 
power  of  the  blood  is  brought  into  play.  Thus  the  blood 
is  consumed.  But  the  whole  body,  though  more  slowly 
than  the  blood,  wastes  also,  so  that  after  a  certain  number 
of  years  it  is  entirely  renewed.  How  is  the  sense  of  per- 
sonal identity  maintained  across  this  flight  of  molecules? 
To  man,  as  we  know  him,  matter  is  necessary  to  conscious- 
ness ;  but  the  matter  of  any  period  may  be  all  changed, 
while  consciousness  exhibits  no  solution  of  continuity. 
Like  changing  sentinels,  the  oxygen,  hydrogen,  and  carbon 
that  depart,  seem  to  whisper  their  secret  to  their  comrades 
that  arrive,  and  thus,  while  the  Non-ego  shifts,  the  Ego  re- 
mains intact.  Constancy  of  form  in  the  grouping  of  the 
molecules,  and  not  constancy  of  the  molecules  themselves, 
is  the  correlative  of  this  constancy  of  perception.  Life 
is  a  wave  which  in  no  two  consecutive  moments  of  its 
existence  is  composed  of  the  same  particles. 

Supposing,  then,  the  molecules  of  the  human  body, 
instead  of  replacing  others,  and  thus  renewing  a  pre- 


404  FRAGMENTS  OP   SCIENCE. 

existing  form,  to  be  gathered  first  hand  from  nature  and 
put  together  in  the  same  relative  positions  as  those  which 
they  occupy  in  the  body.  Supposing  them  to  have  the 
selfsame  forces  and  distribution  of  forces,  the  selfsame 
motions  and  distribution  of  motions — would  this  organised 
concourse  of  molecules  stand  before  us  as  a  sentient 
thinking  being  ?  There  seems  no  valid  reason  to  believe 
that  it  would  not.  Or,  supposing  a  planet  carved  from 
the  sun,  set  spinning  round  an  axis,  and  revolving  round 
the  sun  at  a  distance  from  him  equal  to  that  of  our 
earth,  would  one  of  the  consequences  of  its  refrigera- 
tion be  the  development  of  organic  forms?  I  lean  to  the 
affirmative.  Structural  forces  are  certainly  in  the  mass, 
whether  or  not  those  forces  reach  to  the  extent  of  forming 
a  plant  or  an  animal.  In  an  amorphous  drop  of  water  lie 
latent  all  the  marvels  of  crystalline  force ;  and  who  will 
set  limits  to  the  possible  play  of  molecules  in  a  cooling 
planet  ?  If  these  statements  startle,  it  is  because  m?\ttei 
has  been  denned  and  maligned  by  philosophers  and  theo- 
logians, who  were  equally  unaware  that  it  is,  at  bottom, 
essentially  mystical  and  transcendental. 

Questions  such  as  these  derive  their  present  interest  in 
great  part  from  their  audacity,  which  is  sure,  in  due  time, 
to  disappear.  And  the  sooner  the  public  dread  is  abolished 
with  reference  to  such  questions  the  better  for  the  cause 
of  truth.  As  regards  knowledge,  physical  science  is  polar. 
In  one  sense  it  knows,  or  is  destined  to  know,  everything. 
In  another  sense  it  knows  nothing.  Science  understands 
much  of  this  intermediate  phase  of  things  that  we  call 
nature,  of  which  it  is  the  product ;  but  science  knows 
nothing  of  the  origin  or  destiny  of  nature.  Who  or  what 
made  the  sun,  and  gave  his  rays  their  alleged  power  ? 
Who  or  what  made  and  bestowed  upon  the  ultimate  parti- 
cles of  matter  their  wondrous  power  of  varied  interaction  ? 
Science  does  not  know ;  the  mystery,  though  pushed  back, 


VITALITY.  406 

remaius  unaltered.  To  many  of  us  who  feel  that  there 
are  more  things  in  heaven  and  earth  than  are  dreamt  of  in 
the  present  philosophy  of  science,  but  who  have  been  also 
taught,  by  baffled  efforts,  how  vain  is  the  attempt  to 
grapple  with  the  Inscrutable;  the  ultimate  frame  of  mind 
is  that  of  Goethe : 

Who  dares  to  name  His  name, 

Or  belief  in  Him  proclaim, 

Veiled  in  mystery  as  He  is,  the  All-enfoldor  ? 

Gleams  across  the  mind  His  light, 

Feels  the  lifted  soul  His  might, 

Dare  it  then  deny  His  reign,  the  All-upholder  ? 


All  the  'materialism'  of  the  «  Belfast  Address'  seems 
to  me  to  be  concentrated  in  this  somewhat  ancient  frag- 
ment. 1875. 


i66  FRAGMENTS   OF  SCIENCE, 


VI. 

ON  PRATER  AS  A  FORM  OF  PHYSICAL  ENERGY. 

1872. 

THE  Editor  of  the  'Contemporary  Eeview'  is  liberal 
enough  to  grant  me  space  for  some  remarks  upon  a 
subject,  a  former  reference  to  which  has  brought   down 
upon  me  a  considerable  amount  of  animadversion.1 

It  may  be  interesting  to  some  of  my  readers  if  I  glance 
at  a  few  cases  illustrative  of  the  history  of  the  human 
mind,  in  relation  to  this  and  kindred  questions.  In  the 
fourth  century  the  belief  in  Antipodes  was  deemed  un- 
scriptural  and  heretical.  The  pious  Lactantius  was  as  angry 
with  the  people  who  held  this  notion  as  my  censors  are  now 
with  me,  and  quite  as  unspariog  in  his  denunciations  of  their 
'  Monstrosities.'  Lactantius  was  irritated  because,  in  his 
mind,  by  education  and  habit,  cosmogony  and  religion 
were  indissolubly  associated,  and,  therefore,  simultaneously 
disturbed.  In  the  early  part  of  the  seventeenth  century 
the  notion  that  the  earth  was  fixed,  and  that  the  sun  and 
stars  revolved  round  it  daily,  was  interwoven  with  religious 
feeling,  the  separation  then  attempted  by  Galileo  arousing 
the  animosity  and  kindling  the  persecution  of  the  Church. 
Men  still  living  can  remember  the  indignation  excited 
by  the  first  revelations  of  geology  regarding  the  age  of 
the  earth,  the  association  between  chronology  and  religion 
being  for  the  time  indissoluble.  In  our  day,  however,  the 

1  I  was  made  aware  of  this  by  the  newspapers  which  reached  mo  in 
Switzerland  in  July  1872. 


ON   PRAYER  AS  A  FORM   OF   PHYSICAL   ENERGY.      467 

best-informed  theologians  are  prepared  to  admit  that  our 
views  of  the  Universe  and  its  Author  are  not  impaired, 
but  improved,  by  the  abandonment  of  the  Mosaic  account 
of  the  Creation.  Look,  finally,  at  the  excitement  caused 
by  the  publication  of  the  *  Origin  of  Species ; '  and  com- 
pare it  with  the  calm  attendant  on  the  appearance  of  the 
far  more  outspoken,  and,  from  the  old  point  of  view,  more 
impious,  '  Descent  of  Man.' 

Thus  religion  survives  after  the  removal  of  what  had 
been  long  considered  essential  to  it.  In  our  day  the  Anti- 
podes are  accepted ;  the  fixity  of  the  earth  is  given  up  ; 
the  period  of  Creation  and  the  reputed  age  of  the  world 
are  alike  dissipated;  Evolution  is  looked  upon  without 
terror,  and  other  changes  have  occurred  in  the  same  direc- 
tion too  numerous  to  be  dwelt  upon  here.  In  fact,  from 
the  earliest  times  to  the  present,  religion  has  been  under- 
going a  process  of  purification,  freeing  itself  slowly  and 
painfully  from  the  physical  errors  which  the  active  but 
uninformed  intellect  mingled  with  the  aspirations  of  the 
soul.  Some  of  us  think  that  a  final  act  of  purification  is 
needed,  while  others  oppose  this  notion  with  the  confidence 
and  the  warmth  of  ancient  times.  The  bone  of  conten- 
tion at  present  is  the  physical  value  of  prayer.  It  is  not 
ujy  wish  to  excite  surprise,  much  less  to  draw  forth  protest, 
by  the  employment  of  this  phrase.  I  would  simply  ask 
any  intelligent  person  to  look  the  problem  honestly  in  the 
face,  and  then  to  say  whether,  in  the  estimation  of  the 
great  body  of  those  who  sincerely  resort  to  it,  prayer  does 
not,  at  all  events  upon  special  occasions,  invoke  a  Power 
which  checks  and  augments  the  descent  of  rain,  which 
changes  the  force  and  direction  of  winds,  which  affects  the 
growth  of  corn,  and  the  health  of  men  and  cattle — a  Power, 
in  short,  which,  when  appealed  to  under  pressing  circum- 
stances, produces  the  precise  effects  caused  by  physical 
energy  in  the  ordinary  course  of  things.  To  any  person 


468  FRAGMENTS   OF   SCIENCE. 

who  deals  sincerely  with  the  subject,  and  refuses  to  blur 
his  moral  vision  by  intellectual  subtleties,  this,  I  think,  will 
appear  a  true  statement  of  the  case. 

It  is  under  this  aspect  alone  that  the  scientific  student, 
so  far  as  I  represent  him,  has  any  wish  to  meddle  with 
prayer.  Forced  upon  his  attention  as  a  form  of  physical 
energy,  or  as  the  equivalent  of  such  energy,  he  claims  the 
right  of  subjecting  it  to  those  methods  of  examination 
from  which  all  our  present  knowledge  of  the  physical 
universe  is  derived.  And  if  his  researches  lead  him  to  a 
conclusion  adverse  to  its  claims — if  his  enquiries  rivet  him 
still  closer  to  the  philosophy  implied  in  the  words,  *  He 
maketh  His  sun  to  shine  on  the  evil  and  on  the  good, 
and  sendeth  rain  upon  the  just  and  upon  the  unjust' — he 
contends  only  for  the  displacement  of  prayer,  not  for  its 
extinction.  He  simply  says,  physical  nature  is  not  its 
legitimate  domain. 

This  conclusion,  moreover,  must  be  based  on  pure 
physical  evidence,  and  not  on  any  inherent  unreasonable- 
ness in  the  act  of  prayer.  The  theory  that  the  system  of 
nature  is  under  the  control  of  a  Being  who  changes  phe- 
nomena in  compliance  with  the  prayers  of  men,  is,  in  my 
opinion,  a  perfectly  legitimate  one.  It  may  of  course  be 
rendered  futile  by  being  associated  with  conceptions 
which  contradict  it ;  but  such  conceptions  form  no  neces- 
sary part  of  the  theory.  It  is  a  matter  of  experience  that 
an  earthly  father,  who  is  at  the  same  time  both  wise  and 
tender,  listens  to  the  requests  of  his  children,  and,  if  they 
do  not  ask  amiss,  takes  pleasure  in  granting  their  requests. 
We  know  also  that  this  compliance  extends  to  the  alteration, 
within  certain  limits,  of  the  current  of  events  on  earth. 
With  this  suggestion  offered  by  experience,  it  is  no  de- 
parture from  scientific  method  to  place  behind  natural 
phenomena  a  Universal  Father,  who,  in  answer  to  the 
prayers  of  His  children,  alters  the  currents  of  those  pheno- 


ON   PRATER  AS   A   FORM   OF   PHYSICAL  ENERGT.      469 

mena.  Thus  far  Theology  and  Science  go  hand  in  hand. 
The  conception  of  an  aether,  for  example,  trembling  with 
the  waves  of  light,  is  suggested  by  the  ordinary  phenomena 
of  wave-motion  in  water  and  in  air;  and  in  like  manner 
the  conception  of  personal  volition  in  nature  is  suggested  by 
the  ordinary  action  of  man  upon  earth.  I  therefore  urge  no 
impossibilities,  though  I  am  constantly  charged  with  doing 
so.  I  do  not  even  urge  inconsistency,  but,  on  the  contrary, 
frankly  admit  that  the  theologian  has  as  good  a  right  to 
place  his  conception  at  the  root  of  phenomena  as  I  have  to 
place  mine. 

But  without  verification  a  theoretic  conception  is 
a  mere  figment  of  the  intellect,  and  I  am  sorry  to  find  us 
parting  company  at  this  point.  The  region  of  theory, 
both  in  science  and  theology,  lies  behind  the  world  of 
the  senses,  but  the  verification  of  theory  occurs  in  the 
sensible  world.  To  check  the  theory  we  have  simply  to 
compare  the  deductions  from  it  with  the  facts  of  observa- 
tion. If  the  deductions  be  in  accordance  with  the  facts, 
we  accept  the  theory :  if  in  opposition,  the  theory  is 
given  up.  A  single  experiment  is  frequently  devised,  by 
which  the  theory  must  stand  or  fall.  Of  this  character 
was  the  determination  of  the  velocity  of  light  in  liquids, 
as  a  crucial  test  of  the  Emission  Theory.  According  to 
it,  light  travelled  faster  in  water  than  in  air ;  according 
to  the  Undulatory  Theory,  it  travelled  faster  in  air  than 
in  water.  An  experiment  suggested  by  Arago,  and  exe- 
cuted by  Fizeau  and  Foucault,  was  conclusive  against 
Newton's  theory. 

But,  while  science  cheerfully  submits  to  this  ordeal,  it 
seems  impossible  to  devise  a  mode  of  verification  of  their 
theories  which  does  not  arouse  resentment  in  theological 
minds.  Is  it  that,  while  the  pleasure  of  the  scientific  man 
culminates  in  the  demonstrated  harmony  between  theory 
and  fact,  the  highest  pleasure  of  the  religious  man  haa 


470  FRAGMENTS   OF   SCIENCE. 

been  already  tasted  in  the  very  act  of  praying,  prior  to 
verification,  any  further  effort  in  this  direction  being  a 
mere  disturbance  of  his  peace  ?  Or  is  it  that  we  have 
before  us  a  residue  of  that  mysticism  of  the  middle  ages, 
so  admirably  described  by  Whewell— that  'practice  of 
referring  things  and  events  not  to  clear  and  distinct 
notions,  not  to  general  rules  capable  of  direct  verification, 
but  to  notions  vague,  distant,  and  vast,  which  we  cannot 
bring  into  contact  with  facts;  as  when  we  connect  natural 
events  with  moral  and  historic  causes.'  '  Thus,'  he  con- 
tinues, '  the  character  of  mysticism  is  that  it  refers  parti- 
culars, not  to  generalisations,  homogeneous  and  imme- 
diate, but  to  such  as  are  heterogeneous  and  remote  ;  to 
which  we  must  add  that  the  process  of  this  reference  is 
not  a  calm  act  of  the  intellect,  but  is  accompanied  with  a 
glow  of  enthusiastic  feeling.' 

Every  feature  here  depicted,  and  some  more  question- 
able ones,  have  shown  themselves  of  late ;  most  conspi- 
cuously, I  regret  to  say,  in  the  '  leaders '  of  a  weekly 
journal  of  considerable  influence,  and  one,  on  many 
grounds,  entitled  to  the  respect  of  thoughtful  men.  In 
the  correspondence,  however,  published  by  the  same 
journal,  are  to  be  found  two  or  three  letters  well  calcu- 
lated to  correct  the  temporary  flightiness  of  the  journal 
itself. 

It  is  not  my  habit  of  mind  to  think  otherwise  than 
solemnly  of  the  feeling  which  prompts  prayer.  It  is  a 
power  which  I  should  like  to  see  guided,  not  extin- 
guished— devoted  to  practicable  objects  instead  of  wasted 
upon  air.  In  some  form  or  other,  not  yet  evident,  it 
may,  as  alleged,  be  necessary  to  man's  highest  culture. 
Certain  it  is  that,  while  I  rank  many  persons  who  resort 
to  prayer  low  in  the  scale  of  being— natural  foolishness, 
bigotry,  and  intolerance  being  in  their  case  intensified  by 
the  notion  that  they  have  access  to  the  ear  of  God — I  re- 


ON   PRAYER   AS   A   FORM   OF   PHYSICAL   ENERGY.      471 

gard  others  who  employ  it,  as  forming  part  of  the  very 
cream  of  the  earth.  The  faith  that  adds  to  the  folly 
and  ferocity  of  the  one,  is  turned  to  enduring  sweet- 
ness, holiness,  abounding  charity,  and  self-sacrifice  by  the 
other.  Religion,  in  fact,  varies  with  the  nature  upon  which 
it  falls.  Often  unreasonable,  if  not  contemptible,  prayer, 
in  its  purer  forms,  hints  at  disciplines  which  few  of  us  can 
neglect  without  moral  loss.  But  no  good  can  come  of 
giving  it  a  delusive  value,  by  claiming  for  it  a  power  in 
physical  nature.  It  may  strengthen  the  heart  to  meet 
life's  losses,  and  thus  indirectly  promote  physical  well- 
being,  as  the  digging  of  ^Esop's  orchard  brought  a  treasure 
of  fertility  greater  than  the  golden  treasure  sought.  Such 
indirect  issues  we  all  admit ;  but  it  would  be  simply  dis- 
honest to  affirm  that  it  is  such  issues  that  are  always  in 
view.  Here,  for  the  present,  I  must  end.  I  ask  no  space 
to  reply  to  those  railers  who  make  such  free  use  of  the 
terms  insolence,  outrage,  profanity,  and  blasphemy. 
They  obviously  lack  the  sobriety  of  mind  necessary  to 
give  accuracy  to  their  statements,  or  to  render  their 
charges  worthy  of  serious  refutation. 


472  FRAGMENTS  OF  SCIENCE. 


VII. 
THE  BELFAST  ADDRESS. 

1874. 

AN  impulse  inherent  in  primeval  man  turned  hia 
thoughts  and  questionings  betimes  towards  the 
sources  of  natural  phenomena.  The  same  impulse,  inherited 
and  intensified,  is  the  spur  of  scientific  action  to-day.  Deter 
mined  by  it,  by  a  process  of  abstraction  from  experience  we 
form  physical  theories  which  lie  beyond  the  pale  of  experi- 
ence, but  which  satisfy  the  desire  of  the  mind  to  see  every 
natural  occurrence  resting  upon  a  cause.  In  forming 
their  notions  of  the  origin  of  things,  our  earliest  historic 
(and  doubtless,  we  might  add,  our  prehistoric)  ancestors 
pursued,  as  far  as  their  intelligence  permitted,  the  same 
course.  They  also  fell  back  upon  experience ;  but  with 
this  difference — that  the  particular  experiences  which 
furnished  the  weft  and  woof  of  their  theories  were  drawn, 
not  from  the  study  of  nature,  but  from  what  lay  much 
closer  to  them — the  observation  of  men.  Their  theories 
accordingly  took  an  anthropomorphic  form.  To  super- 
sensual  beings,  which,  *  however  potent  and  invisible, 
were  nothing  but  a  species  of  human  creatures,  perhaps 
raised  from  among  mankind,  and  retaining  all  human 
passions  and  appetites,'1  were  handed  over  the  rule  and 
governance  of  natural  phenomena. 

Tested    by   observation    and    reflection,   these   early 
notions  failed  in  the  long  run  to  satisfy  the  more  pene- 

1  Hume,  '  N.-ittiral  History  of  Eeligion.' 


THE   BELFAST  ADDEESS.  473 

trating  intellects  of  our  race.  Far  in  the  depths  of  his- 
tory we  find  men  of  exceptional  power  differentiating 
themselves  from  the  crowd,  rejecting  these  anthropo- 
morphic notions,  and  seeking  to  connect  natural  pheno- 
mena with  their  physical  principles.  But,  long  prior  to 
these  purer  efforts  of  the  understanding,  the  merchant  had 
been  abroad,  and  rendered  the  philosopher  possible, 
commerce  had  been  developed,  wealth  amassed,  leisure 
for  travel  and  speculation  secured,  while  races  educated 
under  different  conditions,  and  therefore  differently  in- 
formed and  endowed,  had  been  stimulated  and  sharpened 
by  mutual  contact.  In  those  regions  where  the  com- 
mercial aristocracy  of  ancient  Greece  mingled  with  its 
eastern  neighbours,  the  sciences  were  born,  being  nur- 
tured and  developed  by  free-thinking  and  courageous 
men.  The  state  of  things  to  be  displaced  may  be  gathered 
from  a  passage  of  Euripides  quoted  by  Hume.  c  There  is 
nothing  in  the  world ;  no  glory,  no  prosperity.  The  gods 
toss  all  into  confusion ;  mix  everything  with  its  reverse, 
that  all  of  us,  from  our  ignorance  and  uncertainty,  may 
pay  them  the  more  worship  and  reverence.'  Now,  as 
science  demands  the  radical  extirpation  of  caprice,  and  the 
absolute  reliance  upon  law  in  nature,  there  grew,  with  the 
growth  of  scientific  notions,  a  desire  and  determination  to 
sweep  from  the  field  of  theory  this  mob  of  gods  and  de- 
mons, and  to  place  natural  phenomena  on  a  basis  more 
congruent  with  themselves. 

The  problem  which  had  been  previously  approached 
from  above,  was  now  attacked  from  below ;  theoretic 
effort  passed  from  the  super-  to  the  sub-sensible.  It  was 
felt  that  to  construct  the  universe  in  idea,  it  was  necessary 
to  have  some  notion  of  its  constituent  parts — of  what 
Lucretius  subsequently  called  the  *  First  Beginnings.' 
Abstracting  again  from  experience,  the  leaders  of  scientific 
speculation  reached  at  length  the  pregnant  doctrine  of 


474  FRAGMENTS   OF   SCIENCE. 

atoms  and  molecules,  the  latest  developments  of  which  were 
set  forth  with  such  power  and  clearness  at  the  last  meeting 
of  the  British  Association.  Thought,  no  doubt,  had  long 
hovered  about  this  doctrine  before  it  attained  the  preci- 
sion and  completeness  which  it  assumed  in  the  mind  of 
Democritus,1  a  philosopher  who  may  well  for  a  moment 
arrest  our  attention.  '  Few  great  men,'  says  Lange,  a 
non-materialist,  in  his  excellent  '  History  of  Materialism,' 
to  the  spirit  and  to  the  letter  of  which  I  am  equally  in- 
debted, '  have  been  so  despitefully  used  by  history  as 
Democritus.  In  the  distorted  images  sent  down  to  us 
through  unscientific  traditions,  there  remains  of  him  al- 
most nothing  but  the  name  of  "  the  laughing  philosopher," 
while  figures  of  immeasurably  smaller  significance  spread 
themselves  out  at  full  length  before  us.'  Lange  speaks  of 
Bacon's  high  appreciation  of  Democritus — for  ample  illus- 
trations of  which  I  am  indebted  to  my  excellent  friend 
Mr.  Spedding,  the  learned  editor  and  biographer  of  Bacon. 
It  is  evident,  indeed,  that  Bacon  considered  Democritus 
to  be  a  man  of  weightier  metal  than  either  Plato  or 
Aristotle,  though  their  philosophy  '  was  noised  and  cele- 
brated in  the  schools,  amid  the  din  and  pomp  of  pro- 
fessors.' It  was  not  they,  but  Grenseric  and  Attila  and  the 
barbarians,  who  destroyed  the  atomic  philosophy.  '  For,  at 
a  time  when  all  human  learning  had  suffered  shipwreck, 
these  planks  of  Aristotelian  and  Platonic  philosophy,  as 
being  of  a  lighter  and  more  inflated  substance,  were  pre- 
served and  came  down  to  us,  while  things  more  solid  sank 
and  almost  passed  into  oblivion.' 

The  son  of  a  wealthy  father,  Democritus  devoted  the 
whole  of  his  inherited  fortune  to  the  culture  of  his  mind. 
He  travelled  everywhere ;  visited  Athens  when  Socrates 
and  Plato  were  there,  but  quitted  the  city  without 

1  Born  460  B.C. 


THE   BELFAST   ADDRESS.  475 

making  himself  known.  Indeed,  the  dialectic  strife  in 
which  Socrates  so  much  delighted,  had  no  charm  for 
Democritus,  who  held  that  *  the  man  who  readily  contra- 
dicts, and  uses  many  words,  is  unfit  to  learn  anything 
tiuly  right.'  He  is  said  to  have  discovered  and  educated 
Protagoras  the  Sophist,  being  struck  as  much  by  the 
manner  in  which  he,  being  a  hewer  of  wood,  tied  up  his 
faggots,  as  by  the  sagacity  of  his  conversation.  Demo- 
critus returned  poor  from  his  travels,  was  supported  by 
his  brother,  and  at  length  wrote  his  great  work  entitled 
4  Diakosmos,'  which  he  read  publicly  before  the  people  of 
his  native  town.  He  was  honoured  by  his  countrymen  in 
various  ways,  and  died  serenely  at  a  great  age. 

The  principles  enunciated  by  Democritus  reveal  his 
uncompromising  antagonism  to  those  who  deduced  the 
phenomena  of  nature  from  the  caprices  of  the  gods. 
They  are  briefly  these :  1.  From  nothing  comes  nothing. 
Nothing  that  exists  can  be  destroyed.  All  changes  are 
due  to  the  combination  and  separation  of  molecules.  2. 
Nothing  happens  by  chance  :  every  occurrence  has  its 
cause,  from  which  it  follows  by  necessity.  3.  The  only 
existing  things  are  the  atoms  and  empty  space ;  all  else  is 
mere  opinion.  4.  The  atoms  are  infinite  in  number,  and 
infinitely  various  in  form  ;  they  strike  together,  and  the 
lateral  motions  and  whirlings  which  thus  arise  are  the 
beginnings  of  worlds.  5.  The  varieties  of  all  things  de- 
pend upon  the  varieties  of  their  atoms,  in  number,  size, 
and  aggregation.  6.  The  soul  consists  of  fine,  smooth, 
round  atoms,  like  those  of  fire.  These  are  the  most 
mobile  of  all :  they  interpenetrate  the  whole  body,  and 
in  their  motions  the  phenomena  of  life  arise. 

The  first  five  propositions  are  a  fair  general  statement 
of  the  atomic  philosophy,  as  now  held.  As  regards  the 
sixth,  Democritus  made  his  finer  atoms  do  duty  for  the 
nervous  system,  whose  functions  were  then  unknown, 


176  FRAGMENTS   OF   SCIENCE. 

The  atoms  of  Democritus  are  individually  without  sensa- 
tion ;  they  combine  in  obedience  to  mechanical  laws :  and 
not  only  organic  forms,  but  the  phenomena  of  sensation 
and  thought,  are  the  result  of  their  combination. 

That  great  enigma,  c  the  exquisite  adaptation  of  one 
part  of  an  organism  to  another  part,  and  to  the  conditions 
of  life,'  more  especially  the  construction  of  the  human 
body,  Democritus  made  no  attempt  to  solve.  Empedocles, 
a  man  of  more  fiery  and  poetic  nature,  introduced  the 
notion  of  love  and  hate  among  the  atoms,  to  account  for 
their  combination  and  separation.  Noticing  this  gap  in 
the  doctrine  of  Democritus,  he  struck  in  with  the  pene- 
trating thought,  linked,  however,  with  some  wild  specu- 
lation, that  it  lay  in  the  very  nature  of  those  combinations 
which  were  suited  to  their  ends  (in  other  words,  in  har- 
mony with  their  environment)  to  maintain  themselves, 
while  unfit  combinations,  having  no  proper  habitat,  must 
rapidly  disappear.  Thus,  more  than  2,000  years  ago,  the 
doctrine  of  the  '  survival  of  the  fittest,'  which  in  our  day, 
not  on  the  basis  of  vague  conjecture,  but  of  positive 
knowledge,  has  been  raised  to  such  extraordinary  signi- 
ficance, had  received  at  all  events  partial  enunciation.1 

Epicurus,2  said  to  be  the  son  of  a  poor  schoolmaster  at 
Samos,  is  the  next  dominant  figure  in  the  history  of  the 
atomic  philosophy.  He  mastered  the  writings  of  Demo- 
critus, heard  lectures  in  Athens,  went  back  to  Samos,  and 
subsequently  wandered  through  various  countries.  He 
finally  returned  to  Athens,  where  he  bought  a  garden,  and 
surrounded  himself  by  pupils,  in  the  midst  of  whom  he 
lived  a  pure  and  serene  life,  and  died  a  peaceful  death. 
Democritus  looked  to  the  soul  as  the  ennobling  part  of 
man ;  even  beauty,  without  understanding,  partook  of 
animalism.  Epicurus  also  rated  the  spirit  above  the 

1  « Lange,'  2nd  edit.,  p.  23.  *  Born  342  B.C. 


THE   BELFAST  ADDRESS.  477 

body ;  the  pleasure  of  the  body  being  that  of  the  moment, 
while  the  spirit  could  draw  upon  the  future  and  the  past. 
His  philosophy  was  almost  identical  with  that  of  Demo- 
critus ;  but  he  never  quoted  either  friend  or  foe.  One 
main  object  of  Epicurus  was  to  free  the  world  from  super- 
stition and  the  fear  of  death.  Death  he  treated  with 
indifference.  It  merely  robs  us  of  sensation.  As  long  as 
we  are,  death  is  not ;  and  when  death  is,  we  are  not. 
Life  has  no  more  evil  for  him  who  has  made  up  his  mind 
that  it  is  no  evil  not  to  live.  He  adored  the  gods,  but 
not  in  the  ordinary  fashion.  The  idea  of  Divine  power, 
properly  purified,  he  thought  an  elevating  one.  Still  he 
taught,  l  Not  he  is  godless  who  rejects  the  gods  of  the 
crowd,  but  rather  he  who  accepts  them.'  The  gods  were 
to  him  eternal  and  immortal  beings,  whose  blessedness 
excluded  every  thought  of  care  or  occupation  of  any  kind. 
Nature  pursues  her  course  in  accordance  with  everlasting 
laws,  the  gods  never  interfering.  They  haunt 

The  lucid  interspace  of  world  and  world 
Where  never  creeps  a  cloud  or  moves  a  wind, 
Nor  ever  falls  the  least  white  star  of  snow, 
Nor  ever  lowest  roll  of  thunder  moans, 
Nor  sound  of  human  sorrow  mounts  to  mar 
Their  sacred  everlasting  calm.1 

Lange  considers  the  relation  of  Epicurus  to  the  gods 
subjective  ;  the  indication,  probably,  of  an  ethical  require- 
ment of  his  own  nature.  We  cannot  read  history  with 
open  eyes,  or  study  human  nature  to  its  depths,  and  fail 
to  discern  such  a  requirement.  Man  never  has  been,  and 
he  never  will  be,  satisfied  with  the  operations  and  products 
of  the  Understanding  alone;  hence  physical  science  cannot 
cover  all  the  demands  of  his  nature.  But  the  history  of 
the  efforts  made  to  satisfy  these  demands  might  be 
broadly  described  as  a  history  of  errors — the  error,  in 

1  Tennyson's  '  Lucretius.' 


178  FRAGMENTS   OF  SCIENCE. 

great  part,  consisting  in  ascribing  fixity  to  that  which  is 
fluent,  which  varies  as  we  vary,  being  gross  when  we  are 
gross,  and  becoming,  as  our  capacities  widen,  more 
abstract  and  sublime.  On  one  great  point  the  mind  of 
Epicurus  was  at  peace.  He  neither  sought  nor  expected, 
here  or  hereafter,  any  personal  profit  from  his  relation 
to  the  gods.  And  it  is  assuredly  a  fact,  that  loftiness 
and  serenity  of  thought  may  be  promoted  by  conceptions 
which  involve  no  idea  of  profit  of  this  kind.  '  Did  I  not 
believe,'  said  a  great  man  l  to  me  once,  *  that  an  Intelli- 
gence is  at  the  heart  of  things,  my  life  on  earth  would  be 
intolerable.'  The  utterer  of  these  words  is  not,  in  my 
opinion,  rendered  less  but  more  noble  by  the  fact,  that 
it  was  the  need  of  ethical  harmony  here,  and  not  the 
thought  of  personal  profit  hereafter,  that  prompted  his 
observation. 

There  are  persons,  not  belonging  to  the  highest 
intellectual  zone,  nor  yet  to  the  lowest,  to  whom  perfect 
clearness  of  exposition  suggests  want  of  depth.  They 
find  comfort  and  edification  in  an  abstract  and  learned 
pnraseology.  To  such  people  Epicurus,  who  spared  no 
pains  to  rid  his  style  of  every  trace  of  haze  and  tur- 
bidity, appeared,  on  this  very  account,  superficial.  He 
had,  however,  a  disciple  who  thought  it  no  unworthy 
occupation  to  spend  his  days  and  nights  in  the  effort  to 
reach  the  clearness  of  his  master,  and  to  whom  the  Greek 
philosopher  is  mainly  indebted  for  the  extension  and 
perpetuation  of  his  fame.  Some  two  centuries  after  the 
death  of  Epicurus,  Lucretius 2  wrote  his  great  poem,  *  On 
the  Nature  of  Things,'  in  which  he,  a  Eoman,  developed 
with  extraordinary  ardour  the  philosophy  of  his  Greek 
predecessor.  He  wishes  to  win  over  his  friend  Memnius 
to  the  school  of  Epicurus ;  and  although  he  has  no  rewards 

1  Carlyle.  *  Born  09  B.C. 


THE   BELFAST   ADDRESS.  479 

in  a  future  life  to  offer,  although  his  object  appears  to  be 
a  purely  negative  one,  he  addresses  his  friend  with  the 
heat  of  an  apostle.  His  object,  like  that  of  his  great 
forerunner,  is  the  destruction  of  superstition ;  and  con- 
sidering that  men  in  his  day  trembled  before  every 
natural  event  as  a  direct  monition  from  the  gods,  and  that 
everlasting  torture  was  also  in  prospect,  the  freedom 
aimed  at  by  Lucretius  might  be  deemed  a  positive  good. 
*  This  terror,'  he  says,  '  and  darkness  of  mind,  must  be 
dispelled,  not  by  the  rays  of  the  sun  and  glittering  shafts 
of  day,  but  by  the  aspect  and  the  law  of  nature.'  He  re- 
futes the  notion  that  anything  can  come  out  of  nothing, 
or  that  what  is  once  begotten  can  be  recalled  to  nothing. 
The  first  beginnings,  the  atoms,  are  indestructible,  and 
into  them  all  things  can  be  resolved  at  last.  Bodies  are 
partly  atoms  and  partly  combinations  of  atoms ;  but  the 
atoms  nothing  can  quench.  They  are  strong  in  solid 
singleness,  and,  by  their  denser  combination,  all  things 
can  be  closely  packed  and  exhibit  enduring  strength. 
He  denies  that  matter  is  infinitely  divisible.  We  come 
at  length  to  the  atoms,  without  which,  as  an  imperishable 
substratum,  all  order  in  the  generation  and  development 
of  things  would  be  destroyed. 

The  mechanical  shock  of  the  atoms  being,  in  his  view, 
the  all-sufficient  cause  of  things,  he  combats  the  notion 
that  the  constitution  of  nature  has  been  in  any  way  de- 
termined by  intelligent  design.  The  interaction  of  the 
atoms  throughout  infinite  time  rendered  all  manner  of 
combinations  possible.  Of  these,  the  fit  ones  persisted, 
while  the  unfit  ones  disappeared.  Not  after  sage  delibera- 
tion did  the  atoms  station  themselves  in  their  right 
places,  nor  did  they  bargain  what  motions  they  should 
assume.  From  all  eternity  they  have  been  driven  together, 
and,  after  trying  motions  and  unions  of  every  kind,  they 
fell  at  length  into  the  arrangements  out  of  which  this 


480  FRAGMENTS   OP   SCIENCE. 

system  of  things  has  been  evolved.  *  If  you  will  appre- 
hend and  keep  in  mind  these  things,  Nature,  free  at  once, 
and  rid  of  her  haughty  lords,  is  seen  to  do  all  things 
spontaneously  of  herself,  without  the  meddling  of  the 
gods.' 5 

To  meet  the  objection  that  his  atoms  cannot  be  seen, 
Lucretius  describes  a  violent  storm,  and  shows  that  the 
invisible  particles  of  air  act  in  the  same  way  as  the  visible 
particles  of  water.  We  perceive,  moreover,  the  different 
smells  of  things,  yet  never  see  them  coming  to  our  nostrils. 
Again,  clothes  hung  up  on  a  shore,  which  waves  break 
upon,  become  moist,  and  then  get  dry  if  spread  out  in  the 
sun,  though  no  eye  can  see  either  the  approach  or  the 
escape  of  the  water-particles.  A  ring,  worn  long  on  the 
finger,  becomes  thinner ;  a  water-drop  hollows  out  a 
stone ;  the  ploughshare  is  rubbed  away  in  the  field  ;  the 
street-pavement  is  worn  by  the  feet ;  but  the  particles 
that  disappear  at  any  moment  we  cannot  see.  Nature 
acts  through  invisible  particles.  That  Lucretius  had  a 
strong  scientific  imagination  the  foregoing  references 
prove.  A  fine  illustration  of  his  power,  in  this  respect,  is 
his  explanation  of  the  apparent  rest  of  bodies  whose  atoms 
are  in  motion.  He  employs  the  image  of  a  flock  of  sheep 
with  skipping  lambs,  which,  seen  from  a  distance,  pre- 
sents simply  a  white  patch  upon  the  green  hill,  the  jump- 
ing of  the  individual  lambs  being  quite  invisible. 

His  vaguely  grand  conception  of  the  atoms  falling 
eternally  through  space,  suggested  the  nebular  hypothesis 
to  Kant,  its  first  propounder.  Far  beyond  the  limits  of 
our  visible  world  are  to  be  found  atoms  innumerable, 
which  have  never  been  united  to  form  bodies,  or  which, 

1  Monro's  translation.  In  his  criticism  of  this  work  ('  Contemporary 
Eeview,'  1867)  Dr.  Hayman  does  not  appear  to  be  aware  of  the  really 
Bound  and  subtile  observations  on  which  the  reasoning  of  Lucretius,  though 
erroneous,  sometimes  rests. 


THE  BELFAST  ADDKESS.  481 

if  once  united,  have  been  again  dispersed — falling  silently 
through  immeasurable  intervals  of  time  and  space.  As 
everywhere  throughout  the  All  the  same  conditions  are 
repeated,  so  must  the  phenomena  be  repeated  also.  Above 
us,  below  us,  beside  us,  therefore,  are  worlds  without  end ; 
and  this,  when  considered,  must  dissipate  every  thought 
of  a  deflection  of  the  universe  by  the  gods.  The  worlds 
come  and  go,  attracting  new  atoms  out  of  limitless  space, 
or  dispersing  their  own  particles.  The  reputed  death  of 
Lucretius,  which  forms  the  basis  of  Mr.  Tennyson's  noble 
poem,  is  in  strict  accordance  with  his  philosophy,  which 
was  severe  and  pure. 

Still  earlier  than  these  three  philosophers,  and  during 
the  centuries  between  the  first  of  them  and  the  last,  the 
human  intellect  was  active  in  other  fields  than  theirs. 
Pythagoras  had  founded  a  school  of  mathematics,  and 
made  his  experiments  on  the  harmonic  intervals.  The 
Sophists  had  run  through  their  career.  At  Athens  had 
appeared  Socrates,  Plato,  and  Aristotle,  who  ruined  the 
Sophists,  and  whose  yoke  remains  to  some  extent  unbroken 
to  the  present  hour.  Within  this  period  also  the  School 
of  Alexandria  was  founded,  Euclid  wrote  his  '  Elements  ' 
and  made  some  advance  in  optics.  Archimedes  had  pro- 
pounded the  theory  of  the  lever,  and  the  principles  of 
hydrostatics.  Astronomy  was  immensely  enriched  by  the 
discoveries  of  Hipparchus,  who  was  followed  by  the  his- 
torically more  celebrated  Ptolemy.  Anatomy  had  been 
made  the  basis  of  scientific  medicine ;  and  it  is  said  by 
Draper  *  that  vivisection  had  begun.  In  fact,  the  science 
of  ancient  Greece  had  already  cleared  the  world  of  the 
fantastic  images  of  divinities  operating  capriciously 
through  natural  phenomena.  It  had  shaken  itself  free 
from  that  fruitless  scrutiny  '  by  the  internal  light  of  the 

1  '  History  of  the  Intellectual  Development  of  Europe,'  p.  295. 


482  FRAGMENTS   OF   SCIENCE. 

mind  alone,'  which  had  vainly  sought  to  transcend  ex- 
perience, and  to  reach  a  knowledge  of  ultimate  causes. 
Instead  of  accidental  observation,  it  had  introduced  obser- 
vation with  a  purpose ;  instruments  were  employed  to  aid 
the  senses ;  and  scientific  method  was  rendered  in  a  great 
measure  complete  by  the  union  of  Induction  and  Experi- 
ment. 

What,  then,  stopped  its  victorious  advance  ?  Why 
was  the  scientific  intellect  compelled,  like  an  exhausted 
soil,  to  lie  fallow  for  nearly  two  millenniums,  before  it  could 
regather  the  elements  necessary  to  its  fertility  and 
strength  ?  Bacon  has  already  let  us  know  one  cause ; 
Whewell  ascribes  this  stationary  period  to  four  causes — 
obscurity  of  thought,  servility,  intolerance  of  disposition, 
enthusiasm  of  temper  ;  and  he  gives  striking  examples  of 
each.1  But  these  characteristics  must  have  had  their 
antecedents  in  the  circumstances  of  the  time.  Eome, 
and  the  other  cities  of  the  Empire,  had  fallen  into  moral 
putrefaction.  Christianity  had  appeared,  offering  the  gospel 
to  the  poor,  and,  by  moderation,  if  not  asceticism  of  life, 
practically  protesting  against  the  profligacy  of  the  age. 
The  sufferings  of  the  early  Christians,  and  the  extraordinary 
exaltation  of  mind  which  enabled  them  to  triumph  over 
the  diabolical  tortures  to  which  they  were  subjected,2 
must  have  left  traces  not  easily  effaced.  They  scorned 
the  earth,  in  view  of  that  '  building  of  God,  that  house 
not  made  with  hands,  eternal  in  the  heavens.'  The 
Scriptures  which  ministered  to  their  spiritual  needs  were 
also  the  measure  of  their  Science.  When,  for  example, 
the  celebrated  question  of  Antipodes  came  to  be  discussed, 
the  Bible  was  with  many  the  ultimate  court  of  appeal. 
Augustine,  who  flourished  A.D.  400,  would  not  deny  the 
rotundity  of  the  earth ;  but  he  would  deny  the  possible 

1  '  History  of  the  Inductive  Sciences,'  vol.  i. 

*  Depicted  with  terrible  vividness  in  Kenan's  '  Antichrist.' 


THE  BELFAST  ADDRESS.  483 

existence  of  inhabitants  at  the  other  side,  *  because  no 
such  race  is  recorded  in  Scripture  among  the  descendants 
of  Adam.'  Archbishop  Boniface  was  shocked  at  the  as- 
sumption of  a  '  world  of  human  beings  out  of  the  reach  of 
the  means  of  salvation.'  Thus  reined  in,  Science  was 
not  likely  to  make  much  progress.  Later  on,  the  political 
and  theological  strife  between  the  Church  and  civil 
governments,  so  powerfully  depicted  by  Draper,  must 
have  done  much  to  stifle  investigation. 

Whewell  makes  many  wise  and  brave  remarks  re- 
garding the  spirit  of  the  Middle  Ages.  It  was  a  menial 
spirit.  The  seekers  after  natural  knowledge  had  forsaken 
that  fountain  of  living  waters,  the  direct  appeal  to  nature 
by  observation  and  experiment,  and  given  themselves 
up  to  the  remanipulation  of  the  notions  of  their  predeces- 
sors. It  was  a  time  when  thought  had  become  abject,  and 
when  the  acceptance  of  mere  authority  led,  as  it  always 
does  in  science,  to  intellectual  death.  Natural  events, 
instead  of  being  traced  to  physical,  were  referred  to 
moral,  causes ;  while  '  an  exercise '  of  the  phantasy,  almost 
as  degrading  as  the  spiritualism  of  the  present  day,  took 
the  place  of  scientific  speculation.  Then  came  the  mysti- 
cism of  the  Middle  Ages,  Magic,  Alchemy,  the  Neo- 
platonic  philosophy,  with  its  visionary  though  sublime 
abstractions,  which  caused  men  to  look  with  shame  upon 
their  own  bodies,  as  hindrances  to  the  absorption  of  the 
creature  in  the  blessedness  of  the  Creator.  Finally  came 
the  Scholastic  philosophy,  a  fusion,  according  to  Lange, 
of  the  least  mature  notions  of  Aristotle  with  the  Christi- 
anity of  the  west.  Intellectual  immobility  was  the  result. 
Aa  a  traveller  without  a  compass  in  a  fog  may  wander 
long,  imagining  he  is  making  way,  and  find  himself  after 
hours  of  toil  at  his  starting-point,  so  the  schoolmen, 
having  '  tied  and  untied  the  same  knots,  and  formed  and 


484  FEAGMENTS   OF   SCIENCE. 

dissipated  the  same  clouds,'  found  themselves  at  the  end 
of  centuries  in  their  old  position. 

With  regard  to  the  influence  wielded  by  Aristotle  in 
the  Middle  Ages,  and  which,  to  a  less  extent,  he  still 
wields,  I  would  ask  permission  to  make  one  remark. 
When  the  human  mind  has  achieved  greatness  and  given 
evidence  of  extraordinary  power  in  one  domain,  there  is  a 
tendency  to  credit  it  with  similar  power  in  all  other 
domains.  Thus  theologians  have  found  comfort  and  as- 
surance in  the  thought  that  Newton  dealt  with  the  ques- 
tion of  revelation — forgetful  of  the  fact,  that  the  very 
devotion  of  his  powers,  through  all  the  best  years  of  his 
life,  to  a  totally  different  class  of  ideas,  not  to  speak  of 
any  natural  disqualification,  tended  to  render  him  less, 
instead  of  more,  competent  to  deal  with  theological  and 
historic  questions.  Goethe,  starting  from  his  established 
greatness  as  a  poet,  and  indeed  from  his  positive  dis- 
coveries in  Natural  History,  produced  a  profound  impres- 
sion among  the  painters  of  Germany,  when  he  published 
his  *  Farbenlehre,'  in  which  he  endeavoured  to  overthrow 
Newton's  theory  of  colours.  This  theory  he  deemed  so 
obviously  absurd,  that  he  considered  its  author  a  charlatan, 
and  attacked  him  with  a  corresponding  vehemence  of 
language.  In  the  domain  of  natural  history  Groethe  had 
made  really  considerable  discoveries ;  and  we  have  high 
authority  for  assuming  that,  had  he  devoted  himself 
wholly  to  that  side  of  science,  he  might  have  reached,  in 
it,  an  eminence  comparable  with  that  he  attained  as  a 
poet.  In  sharpness  of  observation,  in  the  detection  of 
analogies  apparently  remote,  in  the  classification  and 
organisation  of  facts  according  to  the  analogies  discerned, 
Goethe  possessed  extraordinary  powers.  These  elements 
of  scientific  enquiry  fall  in  with  the  disciplines  of  the 
poet.  But,  on  the  other  hand,  a  mind  thus  richly  en- 
dowed in  the  direction  of  natural  history,  may  be  almost 


THE  BELFAST  ADDKESS.  485 

shorn  of  endowment  as  regards  the  more  strictly  called 
physical  and  mechanical  sciences.  Goethe  was  in  this 
condition.  He  could  not  formulate  distinct  mechanical 
conceptions  ;  he  could  not  see  the  force  of  mechanical 
reasoning ;  and,  in  regions  where  such  reasoning  reigns 
supreme,  he  became  a  mere  ignis  fatuua  to  those  who 
followed  him. 

I  have  sometimes  permitted  myself  to  compare 
Aristotle  with  Goethe — to  credit  the  Stagirite  with  an 
almost  superhuman  power  of  amassing  and  systematising 
facts,  but  to  consider  him  fatally  defective  on  that  side  of 
the  mind,  in  respect  to  which  incompleteness  has  been  just 
ascribed  to  Goethe.  Whewell  refers  the  errors  of  Aristotle 
not  to  a  neglect  of  facts,  but  to  '  a  neglect  of  the  idea 
appropriate  to  the  facts  ;  the  idea  of  Mechanical  cause, 
which  is  Force,  and  the  substitution  of  vague  or  inap- 
plicable notions,  involving  only  relations  of  space  or 
emotions  of  wonder.'  This  is  doubtless  true ;  but  the 
word  'neglect'  implies  mere  intellectual  misdirection, 
whereas  in  Aristotle,  as  in  Goethe,  it  was  not,  I  believe, 
misdirection,  but  sheer  natural  incapacity  which  lay  at 
the  root  of  his  mistakes.  As  a  physicist,  Aristotle  dis- 
played what  we  should  consider  some  of  the  worst  at- 
tributes of  a  modern  physical  investigator — indistinctness 
of  ideas,  confusion  of  mind,  and  a  confident  use  of 
language  which  led  to  the  delusive  notion  that  he  had 
really  mastered  his  subject,  while  he  had,  as  yet,  failed  to 
grasp  even  the  elements  of  it.  He  put  words  in  the 
place  of  things,  subject  in  the  place  of  object.  He  preached 
Induction  without  practising  it,  inverting  the  true  order 
of  enquiry,  by  passing  from  the  general  to  the  particular, 
instead  of  from  the  particular  to  the  general.  He  made 
of  the  universe  a  closed  sphere,  in  the  centre  of  which  he 
fixed  the  earth,  proving  from  general  principles,  to  his 
own  satisfaction  and  to  that  of  the  world  for  near  2,000 


480  FKAGMENTS   OF   SCIENCE. 

'  years,  that  no  other  universe  was  possible.  His  notions 
of  motion  were  entirely  unphysical.  It  was  natural  or 
unnatural,  better  or  worse,  calm  or  violent — no  real  me- 
chanical conception  regarding  it  lying  at  the  bottom  of 
his  mind.  He  affirmed  that  a  vacuum  could  not  exist, 
and  proved  that  if  it  did  motion  in  it  would  be  im- 
possible. He  determined  a  priori  how  many  species  of 
animals  must  exist,  and  shows  on  general  principles  why 
animals  must  have  such  and  such  parts.  When  an 
eminent  contemporary  philosopher,  who  is  far  removed 
from  errors  of  this  kind,  remembers  these  abuses  of  the 
a  priori  method,  he  will  be  able  to  make  allowance  for 
the  jealousy  of  physicists  as  to  the  acceptance  of  so-called 
a  priori  truths.  Aristotle's  errors  of  detail,  as  shown  by 
Eucken  and  Lange,  were  grave  and  numerous.  He 
affirmed  that  only  in  man  we  had  the  beating  of  the 
heart,  that  the  left  side  of  the  body  was  colder  than 
the  right,  that  men  have  more  teeth  than  women,  and 
that  there  is  an  empty  space  at  the  back  of  every  man's 
head. 

There  is  one  essential  quality  in  physical  conceptions, 
which  was  entirely  wanting  in  those  of  Aristotle  and  his 
followers.  I  wish  it  could  be  expressed  by  a  word  un- 
tainted by  its  associations ;  it  signifies  a  capability  of 
being  placed  as  a  coherent  picture  before  the  mind.  The 
Germans  express  the  act  of  picturing  by  the  word 
vorstellen,  and  the  picture  they  call  a  Vorstellung.  We 
have  no  word  in  English  which  comes  nearer  to  our  re- 
quirements than  Imagination ;  and,  taken  with  its  proper 
limitations,  the  word  answers  very  well.  But,  as  just  in- 
timated, it  is  tainted  by  its  associations,  and  therefore 
objectionable  to  some  minds.  Compare,  with  reference 
to  this  capacity  of  mental  presentation,  the  case  of  the 
Aristotelian,  who  refers  the  ascent  of  water  in  a  pump  to 
Nature's  abhorrence  of  a  vacuum,  with  that  of  Pascal 


THE   BELFAST   ADDEESS.  487 

when  lie  proposed  to  solve  the  question  of  atmospheric 
pressure  by  the  ascent  of  the  Puy  de  Dome.  In  the  one 
case  the  terms  of  the  explanation  refuse  to  fall  into  place 
as  a  physical  image  ;  in  the  other  the  image  is  distinct,  the 
descent  and  rise  of  the  barometer  being  clearly  figured  a3 
the  balancing  of  two  varying  and  opposing  pressures. 

During  the  drought  of  the  Middle  Ages  in  Christen- 
dom, the  Arabian  intellect,  as  forcibly  shown  by  Draper, 
was  active.  With  the  intrusion  of  the  Moors  into  Spain, 
order,  learning,  and  refinement  took  the  place  of  their 
opposites.  When  smitten  with  disease,  the  Christian 
peasant  resorted  to  a  shrine,  the  Moorish  one  to  an  in- 
structed physician.  The  Arabs  encouraged  translations 
from  the  Greek  philosophers,  but  not  from  the  Greek 
poets.  They  turned  in  disgust '  from  the  lewdness  of  our 
classical  mythology,  and  denounced  as  an  unpardonable 
blasphemy  all  connection  between  the  impure  Olympian 
Jove  and  the  Most  High  God.'  Draper  traces  still  farther 
than  Whewell  the  Arab  elements  in  our  scientific  terms, 
and  points  out  that  the  under  garment  of  ladies  retains 
to  this  hour  its  Arab  name.  He  gives  examples  of  what 
Arabian  men  of  science  accomplished,  dwelling  particu- 
larly on  Alhazen,  who  was  the  first  to  correct  the  Platonic 
notion  that  rays  of  light  are  emitted  by  the  eye.  Alhazen 
discovered  atmospheric  refraction,  and  showed  that  we  see 
the  sun  and  the  moon  after  they  have  set.  He  explained 
the  enlargement  of  the  sun  and  moon,  and  the  shortening 
of  the  vertical  diameters  of  both  these  bodies  when  near 
the  horizon.  He  was  aware  that  the  atmosphere  decreases 
in  density  with  increase  of  elevation,  and  actually  fixed 
its  height  at  58^  miles.  In  the  '  Book  of  the  Balance 
Wisdom,'  he  sets  forth  the  connection  between  the  weight 
of  the  atmosphere  and  its  increasing  density.  He  showa 
that  a  body  will  weigh  differently  in  a  rare  and  dense 
atmosphere,  and  he  considers  the  force  with  which  plunged 


188  FEAGMENTS   OF   SCIENCE. 

bodies  rise  through  heavier  media.  He  understood  the 
doctrine  of  che  centre  of  gravity,  and  applied  it  to  the 
investigation  of  balances  and  steelyards.  He  recognised 
gravity  as  a  force,  though  he  fell  into  the  error  of 
making  it  diminish  simply  as  the  distance,  and  of 
making  it  purely  terrestrial.  He  knew  the  relation 
between  the  velocities,  spaces,  and  times  of  falling  bodies, 
and  had  distinct  ideas  of  capillary  attraction.  He  improved 
the  hydrometer.  The  determinations  of  the  densities  of 
bodies,  as  given  by  Alhazen,  approach  very  closely  to  our 
own.  '  I  join,'  says  Draper,  in  the  pious  prayer  of  Alhazen, 
'  that  in  the  day  of  judgment  the  All-Merciful  will  take 
pity  on  the  soul  of  Abur-Kaihan,  because  he  was  the  first 
of  the  race  of  men  to  construct  a  table  of  specific  gravi- 
ties.' If  all  this  be  historic  truth  (and  I  have  entire 
confidence  in  Dr.  Draper),  well  may  he  'deplore  the 
systematic  manner  in  which  the  literature  of  Europe  has 
contrived  to  put  out  of  sight  our  scientific  obligations  to 
the  Mahommedans.' l 

The  strain  upon  the  mind  during  the  stationary  period 
towards  ultra-terrestrial  things,  to  the  neglect  of  problems 
close  at  hand,  was  sure  to  provoke  reaction.  But  the  re- 
action was  gradual ;  for  the  ground  was  dangerous,  and  a 
power  at  hand  competent  to  crush  the  critic  who  went  too 
far.  To  elude  this  power,  and  still  allow  opportunity  for 
the  expression  of  opinion,  the  doctrine  of  '  twofold  truth ' 
was  invented,  according  to  which  an  opinion  might  be  held 
'  theologically,'  and  the  opposite  opinion  *  philosophically.' a 
Thus,  in  the  thirteenth  century,  the  creation  of  the  world 
in  six  days,  and  the  unchangeableness  of  the  individual 
soul,  which  had  been  so  distinctly  affirmed  by  St.  Thomas 
Aquinas,  were  both  denied  philosophically,  but  admitted 
to  be  true  as  articles  of  the  Catholic  faith.  When  Prota- 

1  '  Intellectual  Development  of  Europe,'  p.  359. 
*  'Lange,'  2nd  edit.  pp.  181,  182. 


THE   BELFAST   ADDRESS.  489 

goras  uttered  the  maxim  which  brought  upon  him  so  much 
vituperation,  that  'opposite  assertions  are  equally  true.' 
he  simply  meant  to  affirm  men's  differences  to  be  so 
great,  that  what  was  subjectively  true  to  the  one  might 
be  subjectively  untrue  to  the  other.  The  great  Sophist 
never  meant  to  play  fast  and  loose  with  the  truth  by  saying 
that  one  of  two  opposite  assertions,  made  by  the  same 
individual,  could  possibly  escape  being  a  lie.  It  was  not 
'sophistry,'  but  the  dread  of  theologic  vengeance,  that 
generated  this  double  dealing  with  conviction ;  and  it  is 
astonishing  to  notice  what  lengths  were  possible  to  men 
who  were  adroit  in  the  use  of  artifices  of  this  kind. 

Towards  the  close  of  the  stationary  period  a  word-weari- 
ness, if  I  may  so  express  it,  took  more  and  more  possession  of 
men's  minds.  Christendom  had  become  sick' of  the  School 
Philosophy  and  its  verbal  wastes,  which  led  to  no  issue,  but 
left  the  intellect  in  everlasting  haze.  Here  and  there  was 
heard  the  voice  of  one  impatiently  crying  in  the  wilderness, 
'  Not  unto  Aristotle,  not  unto  subtle  hypothesis,  not  unto 
church,  Bible,  or  blind  tradition,  must  we  turn  for  a  know- 
Ledge  of  the  universe,  but  to  the  direct  investigation  of 
nature  by  observation  and  experiment.'  In  1543  the  epoch- 
making  work  of  Copernicus  on  the  paths  of  the  heavenly 
bodies  appeared.  The  total  crash  of  Aristotle's  closed  uni- 
verse, with  the  earth  at  its  centre,  followed  as  a  conse- 
quence; and  'the  earth  moves'  became  a  kind  of  watchword 
among  intellectual  freemen.  Copernicus  was  Canon  of  the 
church  of  Frauenburg  in  the  diocese  of  Ermeland.  For 
three-and-thirty  years  he  had  withdrawn  himself  from  the 
world,  and  devoted  himself  to  the  consolidation  of  his  great 
Bcheme  of  the  solar  system.  He  made  its  blocks  eternal ; 
and  even  to  those  who  feared  it,  and  desired  its  overthrow, 
it  was  so  obviously  strong,  that  they  refrained  for  a  time 
from  meddling  with  it.  In  the  last  year  of  the  life  of 
Copernicus  his  book  appeared  :  it  is  said  that  the  old  man 


490  FRAGMENTS    OF   SCIENCE. 

received  a  copy  of  it  a  few  days  before  his  death,  and  then 
departed  in  peace. 

The  Italian  philosopher,  Giordano  Bruno,  was  one  of  the 
earliest  converts  to  the  new  astronomy.  Taking  Lucretius 
as  his  exemplar,  he  revived  the  notion  of  the  infinity  of 
worlds  ;  and,  combining  with  it  the  doctrine  of  Copernicus, 
reached  the  sublime  generalisation  that  the  fixed  stars  are 
suns,  scattered  numberless  through  space,  and  accompanied 
by  satellites,  which  bear  the  same  relation  to  them  that  our 
earth  does  to  our  sun,  or  our  moon  to  our  earth.  This  was 
an  expansion  of  transcendent  import;  but  Bruno  came  closer 
than  this  to  our  present  line  of  thought.  Struck  with  the 
problem  of  the  generation  and  maintenance  of  organisms, 
and  duly  pondering  it,  he  came  to  the  conclusion  that 
Nature,  in  her  productions,  does  not  imitate  the  technic  of 
man.  Her  process  is  one  of  unravelling  and  unfolding. 
The  infinity  of  forms  under  which  matter  appears  was  not 
imposed  upon  it  by  an  external  artificer ;  by  its  own  intrin- 
sic force  and  virtue  it  brings  these  forms  forth.  Matter  is 
not  the  mere  naked,  empty  capacity  which  philosophers 
have  pictured  her  to  be,  but  the  universal  mother,  who 
brings  forth  all  things  as  the  fruit  of  her  own  womb. 

This  outspoken  man  was  originally  a  Dominican  monk. 
He  was  accused  of  heresy  and  had  to  fly,  seeking  refuge  in 
Geneva,  Paris,  England,  and  Germany.  In  1592  he  fell 
into  the  hands  of  the  Inquisition  at  Venice.  He  was  im- 
prisoned for  many  years,  tried,  degraded,  excommunicated, 
and  handed  over  to  the  Civil  power,  with  the  request  that 
he  should  be  treated  gently,  and  *  without  the  shedding 
of  blood.'  This  meant  that  he  was  to  be  burnt;  and 
burnt  accordingly  he  wa*,  on  February  16,  1600.  To 
escape  a  similar  fate  Galileo,  thirty-three  years  afterwards, 
abjured  upon  his  knees,  with  his  hands  upon  the  holy 
gospels,  the  heliocentric  doctrine,  which  he  knew  to  be  true. 
After  Galileo  came  Kepler,  who  from  his  German  home 


THE   BELFAST   ADDRESS.  491 

defied  the  ultramontane  power.  He  traced  out  from 
pre-existing  observations  the  laws  of  planetary  motion. 
Materials  were  thus  prepared  for  Newton,  who  bound  those 
empirical  laws  together  by  the  principle  of  gravitation. 

In  the  seventeenth  century  Bacon  and  Descartes,  the 
restorers  of  philosophy,  appeared  in  succession.  Differently 
educated  and  endowed,  their  philosophic  tendencies  were 
different.  Bacon  held  fast  to  Induction,  believing  firmly  in 
the  existence  of  an  external  world,  and  making  collected 
experiences  the  basis  of  all  knowledge.  The  mathematical 
studies  of  Descartes  gave  him  a  bias  towards  Deduction ; 
and  his  fundamental  principle  was  much  the  same  as  that 
of  Protagoras,  who  made  the  individual  man  the  measure 
of  all  things.  'I  think,  therefore  I  am,'  said  Descartes. 
Only  his  own  identity  was  sure  to  him ;  and  the  full  deve- 
lopment of  this  system  would  have  led  to  an  idealism,  in 
which  the  outer  world  would  be  resolved  into  a  mere  phe- 
nomenon of  consciousness.  Gassendi,  one  of  Descartes's 
contemporaries,  of  whom  we  shall  hear  more  presently, 
quickly  pointed  out  that  the  fact  of  personal  existence 
would  be  proved  as  well  by  reference  to  any  other  act,  as 
to  the  act  of  thinking.  I  eat,  therefore  I  am  ;  or  I  love, 
therefore  I  am,  would  be  quite  as  conclusive.  Lichten- 
berg,  indeed,  showed  that  the  very  thing  to  be  proved  was 
inevitably  postulated  on  the  first  two  words,  '  I  think  ;'  and 
it  is  plain  that  no  inference  from  the  postulate  could, 
by  any  possibility,  be  stronger  than  the  postulate  itself. 

But  Descartes  deviated  strangely  from  the  idealism 
implied  in  his  fundamental  principle.  He  was  the  first 
to  reduce,  in  a  manner  eminently  capable  of  bearing  the 
test  of  mental  presentation,  vital  phenomena  to  purely 
mechanical  principles.  Through  fear  or  love,  Descartes 
was  a  good  churchman ;  he  accordingly  rejected  the  notion 
of  an  atom,  because  it  was  absurd  to  suppose  that  God, 
if  He  so  pleased,  could  not  divide  an  atom ;  he  puts  in  the 


183  FRAGMENTS   OP   SCIENCE. 

place  of  the  atoms  small  round  particles,  and  light  splinters, 
out  of  which  he  builds  the  organism.  He  sketches  with 
marvellous  physical  insight  a  machine,  with  water  for  its 
motive  power,  which  shall  illustrate  vital  actions.  He  has 
made  clear  to  his  mind  that  such  a  machine  would  be 
competent  to  carry  on  the  processes  of  digestion,  nutrition, 
growth,  respiration,  and  the  beating  of  the  heart.  It 
would  be  competent  to  accept  impressions  from  the  external 
sense,  to  store  them  up  in  imagination  and  memory,  to  go 
through  the  internal  movements  of  the  appetites  and 
passions,  and  the  external  movements  of  the  limbs.  He 
deduces  these  functions  of  his  machine  from  the  mere  ar- 
rangements of  its  organs,  as  the  movement  of  a  clock,  or 
other  automaton,  is  deduced  from  its  weights  and  wheels. 
'  As  far  as  these  functions  are  concerned,'  he  says,  '  it  is 
not  necessary  to  conceive  any  other  vegetative  or  sensitive 
soul,  nor  any  other  principle  of  motion  or  of  life,  than  the 
blood  and  the  spirits  agitated  by  the  fireAvhich  burns  con- 
tinually in  the  heart,  and  which  is  in  nowise  different 
from  the  fires  existing  in  inanimate  bodies.'  Had  Descartes 
been  acquainted  with  the  steam-engine,  he  would  have 
taken  it,  instead  of  a  fall  of  water,  as  his  motive  power. 
He  would  have  shown  the  perfect  analogy  which  exists  be- 
tween the  oxidation  of  the  food  in  the  body,  and  that  of  the 
coal  in  the  furnace.  He  would  assuredly  have  anticipated 
Mayer  in  calling  the  blood  which  the  heart  diffuses,  '  the 
oil  of  the  lamp  of  life  ; '  deducing  all  animal  motions 
from  the  combustion  of  this  oil,  as  the  motions  of  a  steam- 
engine  are  deduced  from  the  combustion  of  its  coal.  As 
the  matter  stands,  however,  and  considering  the  circum- 
stances of  the  time,  the  boldness,  clearness,  and  precision 
with  which  Descartes  grasped  the  problem  of  vital  dynamics 
constitute  a  marvellous  illustration  of  intellectual  power.1 

1  See  Huxley's  admirable  'Essay  on  Descartes.'     ' Lay  Sermons,' pp. 
864,  365. 


THE   BELFAST    ADDEESS .  493 

During  the  Middle  Ages  the  doctrine  of  atoms  had  to 
all  appearance  vanished  from  discussion.  In  all  probability 
it  held  its  ground  among  sober-minded  and  thoughtful 
men,  though  neither  the  church  nor  the  world  was  pre- 
pared to  hear  of  it  with  tolerance.  Once,  in  the  year  1348, 
it  received  distinct  expression.  But  retractation  by  com- 
pulsion immediately  followed ;  and,  thus  discouraged,  it 
slumbered  till  the  seventeenth  century,  when  it  was  re- 
vived by  a  contemporary,  and  friend,  of  Hobbes  of  Malmes- 
bury,  the  orthodox  Catholic  provost  of  Digne,  Gassendi. 
But,  before  stating  his  relation  to  the  Epicurean  doctrine, 
it  will  be  well  to  say  a  few  words  on  the  effect,  as  regards 
science,  of  the  general  introduction  of  monotheism  among 
European  nations. 

*  Were  men,'  says  Hume,  '  led  into  the  apprehension  of 
invisible  intelligent  power  by  contemplation  of  the  works 
of  Nature,  they  could  never  possibly  entertain  any  con- 
ception but  of  one  single  Being,  who  bestowed  existence 
and  order  on  this  vast  machine,  and  adjusted  all  its  parts 
to  one  regular  system.'  Referring  to  the  condition  of  the 
heathen,  who  sees  a  god  behind  every  natural  event,  thus 
peopling  the  world  with  thousands  of  beings  whose  ca- 
prices are  incalculable,  Lange  shows  the  impossibility 
of  any  compromise  between  such  notions  and  those  of 
science,  which  proceeds  on  the  assumption  of  never-changing 
law  and  causality.  'But,'  he  continues,  with  characteristic 
penetration,  l  when  the  great  thought  of  one  God,  acting 
as  a  unit  upon  the  universe,  has  been  seized,  the  connection 
of  things  in  accordance  with  the  law  of  cause  and  effect 
is  not  only  thinkable,  but  it  is  a  necessary  consequence  of 
the  assumption.  For  when  I  see  ten  thousand  wheels  in 
motion,  and  know,  or  believe,  that  they  are  all  driven  by 
one  motive  power,  then  I  know  that  I  have  before  me  a 
mechanism,  the  action  of  every  part  of  which  is  determined 
oy  the  plan  of  the  whole.  So  much  being  assumed,  it  follows 


194  FRAGMENTS   OF   SCIENCE. 

that  I  may  investigate  the  structure  of  that  machine,  and 
the  various  motions  of  its  parts.  For  the  time  being, 
therefore,  this  conception  renders  scientific  action  free.' 
In  other  words,  were  a  capricious  God  at  the  circumference 
of  every  wheel  and  at  the  end  of  every  lever,  the  action 
of  the  machine  would  be  incalculable  by  the  methods  of 
science.  But  the  actions  of  all  its  parts  being  rigidly  deter- 
mined by  their  connections  and  relations,  and  these  being 
brought  into  play  by  a  single  motive  power,  then, 
though  this  last  prime  mover  may  elude  me,  I  am  still 
able  to  comprehend  the  machinery  which  it  sets  in  motion. 
We  have  here  a  conception  of  the  relation  of  Nature  to  its 
Author,  which  seems  perfectly  acceptable  to  some  minds, 
but  perfectly  intolerable  to  others.  Newton  and  Boyle 
lived  and  worked  happily  under  the  influence  of  this  con- 
ception; Goethe  rejected  it  with  vehemence,  and  the  same 
repugnance  to  accepting  it  is  manifest  in  Carlyle.1 

The  analytic  and  synthetic  tendencies  of  the  human 
mind  are  traceable  throughout  history,  great  writers 
ranging  themselves  sometimes  on  the  one  side,  sometimes 
on  the  other.  Men  of  warm  feelings,  and  minds  open  to 
the  elevating  impressions  produced  by  nature  as  a  whole, 
whose  satisfaction,  therefore,  is  rather  ethical  than  logical, 
lean  to  the  synthetic  side  ;  while  the  analytic  harmonises 
best  with  the  more  precise  and  more  mechanical  bias  which 
seeks  the  satisfaction  of  the  understanding.  Some  form 
of  pantheism  was  usually  adopted  by  the  one,  while  a  de- 
tached Creator,  working  more  or  less  after  the  manner  of 
men,  was  often  assumed  by  the  other.  Gassendi,  as 
sketched  by  Lange,  is  hardly  to  be  ranked  with  either 

1  Boyle's  model  of  the  universe  was  the  Strasburg  clock  with  an  outside 
Artificer.  Goethe,  on  the  other  hand,  sang — 

'  Ihm  ziemt's  die  Welt  im  Innern  zu  bewegen, 

Natur  in  sich,  sieh  in  Natur  zu  hegen.' 
See  also  Carlyle,  '  Past  ind  Present,'  chap.  v. 


THE   BELFAST  ADDRESS.  496 

Having  formally  acknowledged  God  as  the  great  first  cause, 
he  immediately  dropped  the  idea,  applied  the  known  laws 
of  mechanics  to  the  atoms,  and  deduced  from  them  all 
vital  phenomena.  He  defended  Epicurus,  and  dwelt  upon 
his  purity,  both  of  doctrine  and  of  life.  True  he  was 
a  heathen,  but  so  was  Aristotle.  Epicurus  assailed  super- 
stition and  religion,  and  rightly,  because  he  did  not  know 
the  true  religion.  He  thought  that  the  gods  neither  re- 
warded nor  punished,  and  he  adored  them  purely  in  conse- 
quence of  their  completeness  :  here  we  see,  says  Gassendi, 
the  reverence  of  the  child,  instead  of  the  fear  of  the  slave. 
The  errors  of  Epicurus  shall  be  corrected,  and  the  body  of 
his  truth  retained.  Gassendi  then  proceeds,  as  any  heathen 
might  do,  to  build  up  the  world,  and  all  that  therein  is,  of 
atoms  and  molecules.  God,  who  created  earth  and  water, 
plants  and  animals,  produced  in  the  first  place  a  definite 
number  of  atoms,  which  constituted  the  seed  of  all  things. 
Then  began  that  series  of  combinations  and  decompo- 
sitions which  now  goes  on,  and  which  will  continue  in 
future.  The  principle  of  every  change  resides  in  matter. 
In  artificial  productions  the  moving  principle  is  different 
from  the  material  worked  upon ;  but  in  nature  the  agent 
works  within,  being  the  most  active  and  mobile  part  of 
the  material  itself.  Thus  this  bold  ecclesiastic,  without 
incurring  the  censure  of  the  church  or  the  world,  contrives 
to  outstrip  Mr.  Darwin.  The  same  cast  of  mind  which 
caused  him  to  detach  the  Creator  from  his  universe,  led 
him  also  to  detach  the  soul  from  the  body,  though  to  the 
body  he  ascribes  an  influence  so  large  as  to  render  the 
soul  almost  unnecessary.  The  aberrations  of  reason  were, 
in  his  view,  an  affair  of  the  material  brain.  Mental  disease 
is  brain-disease  ;  but  then  the  immortal  reason  sits  apart, 
and  cannot  be  touched  by  the  disease.  The  errors  of 
madness  are  those  of  the  instrument,  not  of  the  performer. 
It  may  be  more  than  a  mere  result  of  education,  connect- 


490  FRAGMENTS   OF   SCIENCE. 

ing  itself,  probably,  with  the  deeper  mental  structure  of  the 
two  men,  that  the  idea  of  Gassendi,  above  enunciated,  i8 
substantially  the  same  as  that  expressed  by  Professor  Clerk 
Maxwell,  at  the  close  of  the  very  able  lecture  delivered  by 
him  at  Bradford  last  year.  According  to  both  philoso- 
phers, the  atoms,  if  I  understand  aright,  are  prepared 
materials,  which,  formed  once  for  all  by  the  Eternal,  pro- 
duce by  their  subsequent  interaction  all  the  phenomena  of 
the  material  world.  There  seems  to  be  this  difference,  how- 
ever, between  Gassendi  and  Maxwell.  The  one  postulates, 
the  other  infers  his  firet  cause.  In  his  '  manufactured 
articles,'  as  he  calls  the  atoms,  Professor  Maxwell  finds 
the  basis  of  an  induction,  which  enables  him  to  scale 
philosophic  heights  considered  inaccessible  by  Kant,  and 
to  take  the  logical  step  from  the  atoms  to  their  Maker. 

Accepting  here  the  leadership  of  Kant,  I  doubt  the 
legitimacy  of  Maxwell's  logic  ;  but  it  is  impossible  not  to 
feel  the  ethic  glow  with  which  his  lecture  concludes. 
There  is,  moreover,  a  very  noble  strain  of  eloquence  in  his 
description  of  the  steadfastness  of  the  atoms :  '  Natural 
causes,  as  we  know,  are  at  work,  which  tend  to  modify,  if 
they  do  not  at  length  destroy,  all  the  arrangements  and 
dimensions  of  the  earth  and  the  whole  solar  system.  But 
though  in  the  course  of  ages  catastrophes  have  occurred 
and  may  yet  occur  in  the  heavens,  though  ancient  systems 
may  be  dissolved  and  new  systems  evolved  out  of  their 
ruins,  the  molecules  out  of  which  these  systems  are  built — 
the  foundation  stones  of  the  material  universe — remain 
unbroken  and  unworn.' 

The  atomic  doctrine,  in  whole  or  in  part,  was  enter- 
tained by  Bacon,  Descartes,  Hobbes,  Locke,  Newton,  Boyle, 
and  thrir  successors,  until  the  chemical  law  of  multiple 
proportions  enabled  Dal  ton  to  confer  upon  it  an  entirely 
new  significance.  In  our  day  there  are  secessions  from 
the  theory,  but  it  still  stands  firm.  Loschmidt,  Stoney. 


THE    BELFAST  ADDRESS.  497 

and  Sir  William  Thomson  have  sought  to  determine  the 
sizes  of  the  atoms,  or  rather  to  fix  the  limits  between 
which  their  sizes  lie ;  while  only  last  year  the  discourses 
of  Williamson  and  Maxwell  illustrate  the  present  hold  of 
the  doctrine  upon  the  foremost  scientific  minds.  In  fact, 
it  may  be  doubted  whether,  wanting  this  fundamental  con- 
ception, a  theory  of  the  material  universe  is  capable  of 
scientific  statement. 

Ninety  years  subsequent  to  Gassendi  the  doctrine  of 
bodily  instruments,  as  it  may  be  called,  assumed  immense 
importance  in  the  hands  of  Bishop  Butler,  who,  in  his 
famous  *  Analogy  of  Eeligion,'  developed,  from  his  own 
point  of  view,  and  with  consummate  sagacity,  a  similar 
idea.  The  Bishop  still  influences  superior  minds ;  and  it 
will  repay  us  to  dwell  for  a  moment  on  his  views.  He 
draws  the  sharpest  distinction  between  our  real  selves 
and  our  bodily  instruments.  He  does  not,  as  far  as  I  re- 
member, use  the  word  soul,  possibly  because  the  term  was 
so  hackneyed  in  his  day,  as  it  had  been  for  many  genera- 
tions previously.  But  he  speaks  of  '  living  powers,' 
*  perceiving  or  percipient  powers,'  '  moving  agents,' 
'  ourselves,'  in  the  same  sense  as  we  should  employ  the 
term  soul.  He  dwells  upon  the  fact  that  limbs  may  be 
removed  and  mortal  diseases  assail  the  body,  the  mind, 
almost  up  to  the  moment  of  death,  remaining  clear.  He 
refers  to  sleep  and  to  swoon,  where  the  '  living  powers ' 
are  suspended  but  not  destroyed.  He  considers  it  quite 
as  easy  to  conceive  of  existence  out  of  our  bodies  as  in 
them ;  that  we  may  animate  a  succession  of  bodies,  the 
dissolution  of  all  of  them  having  no  more  tendency  to 
dissolve  our  real  selves,  or  '  deprive  us  of  living  faculties 
— the  faculties  of  perception  and  action — than  the  dis- 
solution of  any  foreign  matter  which  we  are  capable  of 
receiving  impressions  from,  or  making  use  of  for  the 
common  occasions  of  life.'  This  is  the  key  of  the  Bishop's 


t98  FRAGMENTS   OF   SCIENCE. 

position  :  '  our  organised  bodies  are  no  more  a  part  of 
ourselves  than  any  other  matter  around  us.'  In  proof  of 
this  he  calls  attention  to  the  use  of  glasses,  which  'prepare 
objects '  for  the  '  percipient  power '  exactly  as  the  eye 
does.  The  eye  itself  is  no  more  percipient  than  the  glass ; 
is  quite  as  much  the  instrument  of  the  true  self,  and  also 
as  foreign  to  the  true  self,  as  the  glass  is.  '  And  if  we 
see  with  our  eyes  only  in  the  same  manner  as  we  do  with 
glasses,  the  like  may  justly  be  concluded  from  analogy  of 
all  our  senses.' 

Lucretius,  as  you  are  aware,  reached  a  precisely  oppo- 
site conclusion:  and  it  certainly  would  be  interesting,  if  not 
profitable,  to  us  all,  to  hear  what  he  would  or  could  urge 
in  opposition  to  the  reasoning  of  the  Bishop.  As  a  brief 
discussion  of  the  point  will  enable  us  to  see  the  bearings 
of  an  important  question,  I  will  here  permit  a  disciple  of 
Lucretius  to  try  the  strength  of  the  Bishop's  position,  and 
then  allow  the  Bishop  to  retaliate,  with  the  view  of  rolling 
back,  if  he  can,  the  difficulty  upon  Lucretius. 

The  argument  might  proceed  in  this  fashion : — 
'Subjected  to  the  test  of  mental  presentation  (For- 
stellung},  your  views,  most  honoured  prelate,  would  present 
to  many  minds  a  great,  if  not  an  insuperable,  difficulty. 
You  speak  of  "  living  powers,"  "  percipient  or  perceiving 
powers,"  and  "ourselves;"  but  can  you  forma  mental 
picture  of  any  of  these,  apart  from  the  organism  through 
which  it  is  supposed  to  act  ?  Test  yourself  honestly,  and 
see  whether  you  possess  any  faculty  that  would  enable  you 
to  form  such  a  conception.  The  true  self  has  a  local  habit- 
ation in  each  of  us ;  thus  localised,  must  it  not  possess  a 
form  ?  If  so,  what  form  ?  Have  you  ever  for  a  moment 
realised  it  ?  When  a  leg  is  amputated  the  body  is  divided 
into  two  parts  ;  is  the  true  self  in  both  of  them  or  in  one  ? 
Thomas  Aquinas  might  say  in  both  ;  but  not  you,  for  you 
appeal  to  the  consciousness  associated  with  one  of  the  two 


THE   BELFAST  ADDRESS.  499 

parts,  to  prove  that  the  other  is  foreign  matter.  Is  con- 
sciousness, then,  a  necessary  element  of  the  true  self  ?  If 
so,  what  do  you  say  to  the  case  of  the  whole  body  being 
deprived  of  consciousness  ?  If  not,  then  on  what  grounds 
do  you  deny  any  portion  of  the  true  self  to  the  severed 
limb  ?  It  seems  very  singular  that,  from  the  beginning 
to  the  end  of  your  admirable  book  (and  no  one  admires 
its  sober  strength  more  than  I  do),  you  never  once  mention 
the  brain  or  nervous  system.  You  begin  at  one  end  of 
the  body,  and  show  that  its  parts  may  be  removed  without 
prejudice  to  the  perceiving  power.  What  if  you  begin  at 
the  other  end,  and  remove,  instead  of  the  leg,  the  brain  ? 
The  body,  as  before,  is  divided  into  two  parts  ;  but  both 
are  now  in  the  same  predicament,  and  neither  can  be  ap- 
pealed to  to  prove  that  the  other  is  foreign  matter.  Or, 
instead  of  going  so  far  as  to  remove  the  brain  itself,  let  a 
certain  portion  of  its  bony  covering  be  removed,  and  let  a 
rhythmic  series  of  pressures  and  relaxations  of  pressure 
be  applied  to  the  soft  substance.  At  every  pressure  "  the 
faculties  of  perception  and  of  action  "  vanish  ;  at  every  re- 
laxation of  pressure  they  are  restored.  Where,  during  the 
intervals  of  pressure,  is  the  perceiving  power  ?  I  once 
had  the  discharge  of  a  large  Leyden  battery  passed  un- 
expectedly through  me  :  I  felt  nothing,  but  was  simply 
blotted  out  of  conscious  existence  for  a  sensible  interval. 
Where  was  my  true  self  during  that  interval  ?  Men  who 
have  recovered  from  lightning-stroke  have  been  much 
longer  in  the  same  state ;  and  indeed  in  cases  of  ordinary 
concussion  of  the  brain,  days  may  elapse  during  which  no 
experience  is  registered  in  consciousness.  Where  is  the 
man  himself  during  the  period  of  insensibility  ?  You 
may  say  that  I  beg  the  question  when  I  assume  the  man 
to  have  been  unconscious,  that  he  was  really  conscious  all 
the  time,  and  has  simply  forgotten  what  had  occurred  to 
aim.  In  reply  to  this,  1  can  only  say  that  no  one  need 


500  FRAGMENTS    OF   SCIENCE. 

shrink  from  the  worst  tortures  that  superstition  ever  in- 
vented, if  only  so  felt  and  so  remembered.  I  do  not  think 
your  theory  of  instruments  goes  at  all  to  the  bottom  of 
the  matter.  A  telegraph-operator  has  his  instruments, 
by  means  of  which  he  converses  with  the  world ;  our 
bodies  possess  a  nervous  system,  which  plays  a  similar 
part  between  the  perceiving  power  and  external  things. 
Cut  the  wires  of  the  operator,  break  his  battery,  demag- 
netise his  needle ;  by  this  means  you  certainly  sever  his 
connection  with  the  world  ;  but,  inasmuch  as  these  are  real 
instruments,  their  destruction  does  not  touch  the  man 
who  uses  them.  The  operator  survives,  and  he  knows 
that  he  survives.  What  is  it,  I  would  ask,  in  the  human 
system  that  answers  to  this  conscious  survival  of  the 
operator  when  the  battery  of  the  brain  is  so  disturbed  as  to 
produce  insensibility,  or  when  it  is  destroyed  altogether  ? 
'  Another  consideration,  which  you  may  consider  slight, 
presses  upon  me  with  some  force.  The  brain  may  change 
from  health  to  disease,  and  through  such  a  change  the 
most  exemplary  man  may  be  converted  into  a  debauchee 
or  a  murderer.  My  very  noble  and  approved  good  master 
had,  as  you  know,  threatenings  of  lewdness  introduced  into 
his  brain  by  his  jealous  wife's  philter  ;  and  sooner  than 
permit  himself  to  run  even  the  risk  of  yielding  to  these 
base  promptings  he  slew  himself.  How  could  the  hand  of 
Lucretius  have  been  thus  turned  against  himself  if  the 
real  Lucretius  remained  as  before  ?  Can  the  brain  or  can 
it  not  act  in  this  distempered  way  without  the  intervention 
of  the  immortal  reason  ?  If  it  can,  then  it  is  a  prime 
mover  which  requires  only  healthy  regulation  to  render  it 
reasonably  self-acting,  and  there  is  no  apparent  need  of 
your  immortal  reason  at  all.  If  it  cannot,  then  the  im- 
mortal reason,  by  its  mischievous  activity  in  operating  upon 
a  broken  instrument,  must  have  the  credit  of  committing 
every  imaginable  extravagance  and  crime.  I  think,  if  you 


THE   BELFAST   ADDRESS.  501 

will  allow  me  to  say  so,  that  the  gravest  consequences  are 
likely  to  flow  from  your  estimate  of  the  body.  To  regard 
the  brain  as  you  would  a  staff  or  an  eyeglass — to  shut  your 
eyes  to  all  its  mystery,  to  the  perfect  correlation  of  its  con- 
dition and  our  consciousness,  to  the  fact  that  a  slight  excess 
or  defect  of  blood  in  it  produces  the  very  swoon  to  which 
you  refei-,  and  that  in  relation  to  it  our  meat,  and  drink,  and 
air,  and  exercise,  have  a  perfectly  transcendental  value  and 
significance — to  forget  all  this  does,  I  think,  open  a  way 
to  innumerable  errors  in  our  habits  of  life,  and  may  possibly, 
in  some  cases,  initiate  and  foster  that  very  disease,  and  con- 
sequent mental  ruin,  which  a  wiser  appreciation  of  this 
mysterious  organ  would  have  avoided.' 

I  can  imagine  the  Bishop  thoughtful  after  hearing  this 
argument.  He  was  not  the  man  to  allow  anger  to  mingle 
with  the  consideration  of  a  point  of  this  kind.  After  due 
reflection,  and  having  strengthened  himself  by  that  honest 
contemplation  of  the  facts  which  was  habitual  with  him, 
and  which  includes  the  desire  to  give  even  adverse  facts 
their  due  weight,  I  can  suppose  the  Bishop  to  proceed  thus  : 
'  You  will  remember  that  in  the  "  Analogy  of  Eeligion,"  of 
which  you  have  so  kindly  spoken,  I  did  not  profess  to  prove 
anything  absolutely,  and  that  I  over  and  over  again  ac- 
knowledged and  insisted  on  the  smallness  of  our  knowledge, 
or  rather  the  depth  of  our  ignorance,  as  regards  the  whole 
system  of  the  universe.  My  object  was  to  show  my  deistical 
friends,  who  set  forth  so  eloquently  the  beauty  and  bene- 
ficence of  Nature  and  the  Euler  thereof,  while  they  had 
nothing  but  scorn  for  the  so-called  absurdities  of  the 
Christian  scheme,  that  they  were  in  no  better  condition 
then  we  were,  and  that,  for  every  difficulty  found  upon  our 
side,  quite  as  great  a  difficulty  was  to  be  found  upon  theirs. 
I  will  now  with  your  permission  adopt  a  similar  line  of 
argument.  You  are  a  Lucretian,  and  from  the  combina- 
tion and  separation  of  insensate  atoms  deduce  all  terrestrial 


502  FRAGMENTS   OF   SCIENCE. 

things,  including  organic  forms  and  their  phenomena. 
Let  me  tell  you  in  the  first  instance  how  far  I  am  prepared 
to  go  with  you.  I  admit  that  you  can  build  crystalline 
forms  out  of  this  play  of  molecular  force  ;  that  the  diamond, 
amethyst,  and  snow-star  are  truly  wonderful  structures 
which  are  thus  produced.  I  will  go  farther  and  acknow- 
ledge that  even  a  tree  or  flower  might  in  this  way  be  or- 
ganised. Nay,  if  you  can  show  me  an  animal  without 
sensation,  I  will  concede  to  you  that  it  also  might  be  put 
together  by  the  suitable  play  of  molecular  force. 

'  Thus  far  our  way  is  clear,  but  now  comes  my  difficulty. 
Your  atoms  are  individually  without  sensation,  much  more 
are  they  without  intelligence.  May  I  ask  you,  then,  to 
try  your  hand  upon  this  problem.  Take  your  dead  hydro- 
gen atoms,  your  dead  oxygen  atoms,  your  dead  carbon 
atoms,  your  dead  nitrogen  atoms,  your  dead  phosphorus 
atoms,  and  all  the  other  atoms,  dead  as  grains  of  shot,  of 
which  the  brain  is  formed.  Imagine  them  separate  and 
sensationless  ;  observe  them  running  together  and  forming 
all  imaginable  combinations.  This,  as  a  purely  mechanical 
process,  is  seeable  by  the  mind.  But  can  you  see,  or  dream, 
or  in  any  way  imagine,  how  out  of  that  mechanical  act,  and 
from  these  individually  dead  atoms,  sensation,  thought,  and 
emotion  are  to  rise  ?  Are  you  likely  to  extract  Homer  out 
of  the  rattling  of  dice,  or  the  Differential  Calculus  out  of 
the  clash  of  billiard-balls  ?  I  am  not  all  bereft  of  this 
Vorstellungs-Kraft  of  which  you  speak,  nor  am  I,  like  so 
many  of  my  brethren,  a  mere  vacuum  as  regards  scientific 
knowledge.  I  can  follow  a  particle  of  musk  until  it  reaches 
the  olfactory  nerve ;  I  can  follow  the  waves  of  sound  until 
their  tremors  reach  the  water  of  the  labyrinth,  and  set  the 
otoliths  and  Corti's  fibres  in  motion  ;  I  can  also  visualise 
the  waves  of  aether  as  they  cross  the  eye  and  hit  the  retina. 
Nay  more,  I  am  able  to  pursue  to  the  central  organ  the 
motion  thus  imparted  at  the  periphery,  and  to  see  in  idea 


THE   BELFAST  ADDRESS.  503 

the  very  molecules  of  the  brain  thrown  into  tremors.  My 
insight  is  not  baffled  by  these  physical  processes.  What 
baffles  and  bewilders  me  is  the  notion  that  from  those 
physical  tremors  things  so  utterly  incongruous  with  them 
as  sensation,  thought,  and  emotion  can  be  derived.  You 
may  say,  or  think,  that  this  issue  of  consciousness  from 
the  clash  of  atoms  is  not  more  incongruous  than  the  flash 
of  light  from  the  union  of  oxygen  and  hydrogen.  But  I 
beg  to  say  that  it  is.  For  such  incongruity  as  the  flash 
possesses  is  that  which  I  now  force  upon  your  attention. 
The  "flash''  is  an  affair  of  consciousness,  the  objective  coun- 
terpart of  which  is  a  vibration.  It  is  a  flash  only  by  your 
interpretation.  You  are  the  cause  of  the  apparent  incon- 
gruity ;  and  you  are  the  thing  that  puzzles  me.  I  need 
not  remind  you  that  the  great  Leibnitz  felt  the  difficulty 
which  I  feel ;  and  that  to  get  rid  of  this  monstrous  deduc- 
tion of  life  from  death  he  displaced  your  atoms  by  hi& 
monads,  which  were  more  or  less  perfect  mirrors  of  the 
universe,  and  out  of  the  summation  and  integration  of 
which  he  supposed  all  the  phenomena  of  life — sentient,  in- 
tellectual, and  emotional — to  arise. 

*  Your  difficulty,  then,  as  I  see  you  are  ready  to  admit, 
13  quite  as  great  as  mine.  You  cannot  satisfy  the  human 
understanding  in  its  demand  for  logical  continuity  between 
molecular  processes  and  the  phenomena  of  consciousness. 
This  is  a  rock  on  which  Materialism  must  inevitably  split- 
whenever  it  pretends  to  be  a  complete  philosophy  of  life. 
What  is  the  moral,  my  Lucretian  ?  You  and  I  are  not 
likely  to  indulge  in  ill-temper  in  the  discussion  of  these 
great  topics,  where  we  see  so  much  room  for  honest  differ- 
ences of  opinion.  But  there  are  people  of  less  wit  or  more 
bigotry  (I  say  it  with  humility),  on  both  sides,  who  are  ever 
ready  to  mingle  anger  and  vituperation  with  such  discus- 
sions. There  are,  for  example,  writers  of  note  and  influence 
at  the  present  day,  who  are  not  ashamed  publicly  to  assume 


504  FRAGMENTS   OF   SCIENCE. 

the  "deep  personal  sin"  of  a  great  logician  to  be  the  cause 
of  his  unbelief  in  a  theologic  dogma.1  And  there  are  others 
who  hold  that  we,  who  cherish  our  noble  Bible,  wrought 
as  it  has  been  into  the  constitution  of  our  forefathers,  and 
by  inheritance  into  us,  must  necessarily  be  hypocritical  and 
insincere.  Let  us  disavow  and  discountenance  such  people, 
cherishing  the  unswerving  faith  that  what  is  good  and  true 
in  both  our  arguments  will  be  preserved  for  the  benefit  of 
humanity,  while  all  that  is  bad  or  false  will  disappear.' 

I  hold  the  Bishop's  reasoning  to  be  unanswerable,  and 
his  liberality  to  be  worthy  of  imitation. 

It  is  worth  remarking  that  in  one  respect  the  Bishop 
was  a  product  of  his  age.  Long  previous  to  his  day  the 
nature  of  the  soul  had  been  so  favourite  and  general  a  topic 
of  discussion,  that,  when  the  students  of  the  Italian  Uni- 
versities wished  to  know  the  leanings  of  a  new  Professor, 
they  at  once  requested  him  to  lecture  upon  the  soul. 
About  the  time  of  Bishop  Butler  the  question  was  not  only 
agitated  but  extended.  It  was  seen  by  the  clear- witted 
men  who  entered  this  arena,  that  many  of  their  best  argu- 
ments applied  equally  to  brutes  and  men.  The  Bishop's 
arguments  were  of  this  character.  He  saw  it,  admitted  it, 
took  the  consequence,  and  boldly  embraced  the  whole 
animal  world  in  his  scheme  of  immortality. 

Bishop  Butler  accepted  with  unwavering  trust  the  chro- 
nology of  the  Old  Testament,  describing  it  as  '  confirmed 
by  the  natural  and  civil  history  of  the  world,  collected 
from  common  historians,  from  the  state  of  the  earth,  and 
from  the  late  inventions  of  arts  and  sciences.'  These 

1  This  is  the  aspect  under  which  the  Editor  of  the  '  Dublin  Review ' 
presents  to  his  readers  the  memory  of  John  Stuart  Mill.  I  can  only  say, 
that  I  would  as  socn  take  my  chance  in  the  other  world,  in  the  company  of 
the  '  unbeliever,'  as  in  that  of  his  Jesuit  detractor.  In  Dr.  "Ward  we  have 
an  example  of  a  wholesome  and  vigorous  nature,  soured  and  perverted  by  a 
poisonous  creed. 


THE   BELFAST   ADD11ESS.  505 

words  mark  progress  ;  and  they  must  seem  somewhat  hoary 
to  the  Bishop's  successors  of  to-day.  It  is  hardly  neces- 
sary to  inform  you  that  since  his  time  the  domain  of  the 
naturalist  has  been  immensely  extended — the  whole  science 
of  geology,  with  its  astounding  revelations  regarding  the 
life  of  the  ancient  earth,  having  been  created.  The 
rigidity  of  old  conceptions  has  been  relaxed,  the  public 
mind  being  rendered  gradually  tolerant  of  the  idea  that 
not  for  six  thousand,  nor  for  sixty  thousand,  nor  for  six 
thousand  thousand,  but  for  seons  embracing  untold  mil- 
lions of  years,  this  earth  has  been  the  theatre  of  life 
and  death.  The  riddle  of  the  rocks  has  been  read  by  the 
geologist  and  palaeontologist,  from  sub-cambrian  depths 
to  the  deposits  thickening  over  the  sea-bottoms  of  to-day. 
And  upon  the  leaves  of  that  stone  book  are,  as  you  know, 
stamped  the  characters,  plainer  and  surer  than  those  formed 
by  the  ink  of  history,  which  carry  the  mind  back  into 
abysses  of  past  time,  compared  with  which  the  periods  which 
satisfied  Bishop  Butler  cease  to  have  a  visual  angle. 

The  lode  of  discovery  once  struck,  those  petrified  forms 
in  which  life  was  at  one  time  active,  increased  to  multi- 
tudes and  demanded  classification.  They  were  grouped  in 
genera,  species,  and  varieties,  according  to  the  degree  of 
similarity  subsisting  between  them.  Thus  confusion  was 
avoided,  each  object  being  found  in  the  pigeon-hole  appro- 
priated to  it  and  to  its  fellows  of  similar  morphological  or 
physiological  character.  The  general  fact  soon  became 
evident  that  none  but  the  simplest  forms  of  life  lie  lowest 
down ;  that,  as  we  climb  higher  among  the  superimposed 
strata,  more  perfect  forms  appear.  The  change,  however, 
from  form  to  form  was  not  continuous,  but  by  steps — some 
small,  some  great.  '  A  section,'  says  Mr.  Huxley,  'a  hun- 
dred feet  thick  will  exhibit  at  different  heights  a  dozen 
species  of  Ammonite,  none  of  which  passes  beyond  its  par- 
ticular zone  of  limestone,  or  clay,  into  the  zone  below  it, 


506  FKAGMENTS   OF   SCIENCE. 

or  into  that  above  it.'  In  the  presence  of  such  facts  it 
was  not  possible  to  avoid  the  question :  Have  these  forms, 
showing,  though  in  broken  stages,  and  with  many  irregu- 
larities, this  unmistakable  general  advance,  been  subjected 
to  no  continuous  law  of  growth  or  variation  ?  Had  our  edu- 
cation been  purely  scientific,  or  had  it  been  sufficiently  de- 
tached from  influences  which,  however  ennobling  in  another 
domain,  have  always  proved  hindrances  and  delusions  when 
introduced  as  factors  into  the  domain  of  physics,  the  scien- 
tific mind  never  could  have  swerved  from  the  search  for 
a  law  of  growth,  or  allowed  itself  to  accept  the  anthropo- 
morphism which  regarded  each  successive  stratum  as  a 
kind  of  mechanic's  bench  for  the  manufacture  of  new  species 
out  of  all  relation  to  the  old. 

Biased,  however,  by  their  previous  education,  the  great 
majority  of  naturalists  invoked  a  special  creative  act  to 
account  for  the  appearance  of  each  new  group  of  organisms. 
Doubtless  numbers  of  them  were  clear-headed  enough 
to  see  that  this  was  no  explanation  at  all — that  in  point 
of  fact  it  was  an  attempt,  by  the  introduction  of  a  greater 
difficulty,  to  account  for  a  less.  But,  having  nothing  to 
offer  in  the  way  of  explanation,  they  for  the  most  part 
held  their  peace.  Still  the  thoughts  of  reflecting  men 
naturally  and  necessarily  simmered  round  the  question. 
De  Maillet,  a  contemporary  of  Newton,  has  been  brought 
into  notice  by  Professor  Huxley  as  one  who  '  had  a  notion 
of  the  modifiability  of  living  forms.'  In  my  frequent  con- 
versations with  the  late  Sir  Benjamin  Brodie,  a  man  of 
highly  philosophic  mind,  he  often  drew  my  attention  to  the 
fact  that,  as  early  as  1794,  Charles  Darwin's  grandfather 
was  the  pioneer  of  Charles  Darwin.1  In  1801,  and  in  subse- 
quent years,  the  celebrated  Lamarck,  who,  through  the 
vigorous  exposition  of  his  views  by  the  author  of  the '  Ves- 
tiges of  Creation,'  rendered  the  public  mind  perfectly  fami- 
liar with  the  idea  of  evolution,  endeavoured  to  show  thede 

1  '  Zo.wmia,'  vol.  i.  pp.  500-510. 


THE  BELFAST  ADDEESS.  507 

velopment  of  species  out  of  changes  of  habit  and  external 
condition.  In  1813  Dr.  Wells,  the  founder  of  our  present 
theory  of  Dew,  read  before  the  Koyal  Society  a  paper  in 
which,  to  use  the  words  of  Mr.  Darwin,  '  he  distinctly 
recognises  the  principle  of  natural  selection  ;  and  this  is 
the  first  recognition  that  has  been  indicated.'  The 
thoroughness  and  skill  with  which  Wells  pursued  his  work, 
and  the  obvious  independence  of  his  character,  rendered  him 
long  ago  a  favourite  with  me ;  and  it  gave  me  the  liveliest 
pleasure  to  alight  upon  this  additional  testimony  to  his 
penetration.  Professor  Grant,  Mr.  Patrick  Matthew, 
Von  Buch,  the  author  of  the  « Vestiges,'  D'Halloy,  and 
others,1  by  the  enunciation  of  opinions  more  or  less  clear 
and  correct,  showed  that  the  question  had  been  fer- 
menting long  prior  to  the  year  1858,  when  Mr.  Darwin 
and  Mr.  Wallace  simultaneously,  but  independently, 
placed  their  closely  concurrent  views  before  the  Linnean 
^ociety. 

These  papers  were  followed  in  1859  by  the  publication 
of  the  first  edition  of  the  '  Origin  of  Species.'  All  great 
things  come  slowly  to  the  birth.  Copernicus,  as  I  in- 
formed you,  pondered  his  great  work  for  thirty-three 
years.  Newton  for  nearly  twenty  years  kept  the  idea  of 
Gravitation  before  his  mind;  for  twenty  years  also  he 
dwelt  upon  his  discovery  of  Fluxions,  and  doubtless 
would  have  continued  to  make  it  the  object  of  his 
private  thought,  had  he  not  found  Leibnitz  upon  his 
track.  Darwin  for  two-and-twenty  years  pondered  the 
problem  of  the  origin  of  species,  and  doubtless  he  would 
have  continued  to  do  so  had  he  not  found  Wallace  upon 
his  track.2  A  concentrated,  but  full  and  powerful,  epitome 

1  In  1855  Mr.  Herbert  Spencer  ('Principles  of  Psychology,'  2nd  edit, 
vol.  i.  p.  465)  expressed  '  the  belief  that  life  under  all  its  forms  has  arisen 
by  an  unbroken  evolution,  and  through  the  instrumentality  of  what  are 
called  natural  causes.'  This  was  my  belief  also  at  that  time. 

*  The  behaviour  of  Mr.  Wallace  :n  relation  to  this  subject  has  been 
dignified  in  the  highest  degree. 
21 


608  FKAGMENTS   OF   SCIENCE. 

of  his  labours  was  the  consequence.  The  book  was  by  no 
means  an  easy  one  ;  and  probably  not  one  in  every  score 
of  those  who  then  attacked  it,  had  read  its  pages  through, 
or  were  competent  to  grasp  their  significance  if  they  had. 
I  do  not  say  this  merely  to  discredit  them :  for  there  were 
in  those  days  some  really  eminent  scientific  men,  entirely 
raised  above  the  heat  of  popular  prejudice,  and  willing  to 
accept  any  conclusion  that  science  had  to  offer,  provided 
it  was  duly  backed  by  fact  and  argument,  who  entirely 
mistook  Mr.  Darwin's  views.  In  fact  the  work  needed  an 
expounder,  and  it  found  one  in  Mr.  Huxley.  I  know 
nothing  more  admirable  in  the  way  of  scientific  exposition 
than  those  early  articles  of  his  on  the  origin  of  species. 
He  swept  the  curve  of  discussion  through  the  really  sig- 
nificant points  of  the  subject,  enriched  his  exposition  with 
profound  original  remarks  and  reflections,  often  summing 
up  in  a  single  pithy  sentence  an  argument  which  a  less 
compact  mind  would  have  spread  over  pages.  But  these 
is  one  impression  made  by  the  book  itself  which  no  expo- 
sition of  it,  however  luminous,  can  convey ;  and  that  is 
the  impression  of  the  vast  amount  of  labour,  both  of  ob- 
servation and  of  thought,  implied  in  its  production.  Let 
us  glance  at  its  principles. 

It  is  conceded  on  all  hands  that  what  are  called 
1  varieties '  are  continually  produced.  The  rule  is  probably 
without  exception.  No  chick,  or  child,  is  in  all  respects 
and  particulars  the  counterpart  of  its  brother  and  sister  ; 
and  in  such  differences  we  have  '  variety '  incipient.  No 
naturalist  could  tell  how  far  this  variation  could  be  carried; 
but  the  great  mass  of  them  held  that  never,  by  any  amount 
of  internal  or  external  change,  nor  by  the  mixture  of  both, 
could  the  offspring  of  the  same  progenitor  so  far  deviate 
from  each  other  as  to  constitute  different  species.  The 
function  of  the  experimental  philosopher  is  to  combine 
the  conditions  of  Nature  and  to  produce  her  results ;  and 


THE   BELFAST   ADDRESS.  509 

this  was  the  method  of  Darwin.1  He  made  himself 
acquainted  with  what  could,  without  any  manner  of  doubt, 
be  done  in  the  way  of  producing  variation.  He  associated 
himself  with  pigeon-fanciers — bought,  begged,  kept,  and 
observed  every  breed  that  he  could  obtain.  Though  de- 
rived from  a  common  stock,  the  diversities  of  these  pigeons 
were  such  that  *  a  score  of  them  might  be  chosen  which, 
if  shown  to  an  ornithologist,  and  he  were  told  that  they 
were  wild  birds,  would  certainly  be  ranked  by  him  as  well- 
defined  species.'  The  simple  principle  which  guides  the 
pigeon-fancier,  as  it  does  the  cattle-breeder,  is  the  se- 
lection of  some  variety  that  strikes  his  fancy,  and  the  pro- 
pagation of  this  variety  by  inheritance.  With  his  eye 
still  directed  to  the  particular  appearance  which  he  wishes 
to  exaggerate,  he  selects  it  as  it  reappears  in  successive 
broods,  and  thus  adds  increment  to  increment  until  an 
astonishing  amount  of  divergence  from  the  parent  type  is 
effected.  The  breeder  in  this  case  does  not  produce  the 
elements  of  the  variation.  He  simply  observes  them,  and  by 
selection  adds  them  together  until  the  required  result  has 
been  obtained.  '  No  man,'  says  Mr.  Darwin, '  would  ever 
try  to  make  a  fantail  till  he  saw  a  pigeon  with  a  tail  de- 
veloped in  some  slight  degree  in  an  unusual  manner,  or  a 
pouter  until  he  saw  a  pigeon  with  a  crop  of  unusual  size.' 
Thus  nature  gives  the  hint,  man  acts  upon  it,  and  by  the 
law  of  inheritance  exaggerates  the  deviation. 

Having  thus  satisfied  himself  by  indubitable  facts  that 
the  organisation  of  an  animal  or  of  a  plant  (for  precisely 
the  same  treatment  applies  to  plants)  is  to  some  extent 
plastic,  he  passes  from  variation  under  domestication  to 
variation  under  nature.  Hitherto  we  have  dealt  with  the 
adding  together  of  small  changes  by  the  conscious  selection 

1  The  first  step  only  towards  experimental  demonstration  has  been 
taken.  Experiments  now  begun  might,  a  couple  of  centuries  hence,  furnish 
data  of  incalculable  value,  which  ought  to  be  supplied  to  the  science  of  the 
future. 


610  FRAGMENTS   OF   SCIENCE. 

of  man.  Can  Nature  thus  select  ?  Mr.  Darwin's  answer 
is,  *  Assuredly  she  can.'  The  number  of  living  things  pro- 
duced is  far  in  excess  of  the  number  that  can  be  sup- 
ported ;  hence  at  some  period  or  other  of  their  lives  there 
must  be  a  struggle  for  existence  ;  and  what  is  the  in- 
fallible result  ?  If  one  organism  were  a  perfect  copy  of 
the  other  in  regard  to  strength,  skill,  and  agility,  external 
conditions  would  decide.  But  this  is  not  the  case.  Here 
we  have  the  fact  of  variety  offering  itself  to  nature,  as  in 
the  former  instance  it  offered  itself  to  man ;  and  those 
varieties  which  are  least  competent  to  cope  with  sur- 
rounding conditions,  will  infallibly  give  way  to  those  that 
are  most  competent.  To  use  a  familiar  proverb,  the 
weakest  comes  to  the  wall.  But  the  triumphant  frac- 
tion again  breeds  to  over-production,  transmitting  the 
qualities  which  secured  its  maintenance,  but  transmitting 
them  in  different  degrees.  The  struggle  for  food  again 
supervenes,  and  those  to  whom  the  favourable  quality 
has  been  transmitted  in  excess,  will  triumph  as  before. 

It  is  easy  to  see  that  we  have  here  the  addition  of  incre- 
ments favourable  to  the  individual,  still  more  rigorously 
carried  out  than  in  the  case  of  domestication ;  for  not 
only  are  unfavourable  specimens  not  selected  by  nature, 
but  they  are  destroyed.  This  is  what  Mr.  Darwin  calls 
'Natural  Selection,'  which  'acts  by  the  preservation 
and  accumulation  of  small  inherited  modifications,  each 
profitable  to  the  preserved  being.'  With  this  idea  he  in- 
terpenetrates and  leavens  the  vast  store  of  facts  that  he 
and  others  have  collected.  "We  cannot,  without  shutting 
our  eyes  through  fear  or  prejudice,  fail  to  see  that  Darwin 
is  here  dealing,  not  with  imaginary,  but  with  true  causes  ; 
nor  can  we  fail  to  discern  what  vast  modifications  may  be 
produced  by  natural  selection  in  periods  sufficiently  long. 
Each  individual  increment  may  resemble  what  mathe- 
maticians call  a  'differential'  (a  quantity  indefinitely 


THE   BELFAST  ADDRESS.  611 

small) ;  but  definite  and  great  changes  may  obviously  be 
produced  by  the  integration  of  these  infinitesimal  quantities, 
through  practically  infinite  time. 

If  Darwin,  like  Bruno,  rejects  the  notion  of  creative 
power  acting  after  human  fashion,  it  certainly  is  not 
because  he  is  unacquainted  with  the  numberless  exquisite 
adaptations,  on  which  this  notion  of  a  supernatural  Artificer 
has  been  founded.  His  book  is  a  repository  of  the  most 
startling  facts  of  this  description.  Take  the  marvellous 
observation  which  he  cites  from  Dr.  Criiger,  where  a 
bucket  with  an  aperture,  serving  as  a  spout,  is  formed  in 
an  orchid.  Bees  visit  the  flower :  in  eager  search  of  material 
for  their  combs  they  push  each  other  into  the  bucket,  the 
drenched  ones  escaping  from  their  involuntary  bath  by  the 
spout.  Here  they  rub  their  backs  against  the  viscid  stigma 
of  the  flower  and  obtain  glue ;  then  against  the  pollen- 
masses,  which  are  thus  stuck  to  the  back  of  the  bee  and  car- 
ried away.  c  When  the  bee,  so  provided,  flies  to  another 
flower,  or  to  the  same  flower  a  second  time,  and  is  pushed 
by  its  comrades  into  the  bucket,  and  then  crawls  out  by 
the  passage,  the  pollen-mass  upon  its  back  necessarily 
comes  first  into  contact  with  the  viscid  stigma,'  which 
takes  up  the  pollen ;  and  this  is  how  that  orchid  is  fertil- 
ised. Or  take  this  other  case  of  the  Cataseium.  '  Bees 
visit  these  flowers  in  order  to  gnaw  the  labellum  ;  in  doing 
this  they  inevitably  touch  a  long,  tapering,  sensitive 
projection.  This,  when  touched,  transmits  a  sensation  or 
vibration  to  a  certain  membrane,  which  is  instantly  rup- 
tured, setting  free  a  spring,  by  which  the  pollen-mass  is 
shot  forth  like  an  arrow  in  the  right  direction,  and  adheres 
by  its  viscid  extremity  to  the  back  of  the  bee.'  In  this 
way  the  fertilising  pollen  is  spread  abroad. 

It  is  the  mind  thus  stored  with  the  choicest  materials 
of  the  teleologist  that  rejects  teleology,  seeking  to  refer 
these  wonders  to  natural  causes.  They  illustrate,  according 


612  FRAGMENTS   OP   SCIENCE. 

to  him,  the  method  of  nature,  not  the  '  technic '  of  a  man- 
like Artificer.  The  beauty  of  flowers  is  due  to  natural 
selection.  Those  that  distinguish  themselves  by  vividly 
contrasting  colours  from  the  surrounding  green  leaves  are 
most  readily  seen,  most  frequently  visited  by  insects,  most 
often  fertilised,  and  hence  most  favoured  by  natural  selec- 
tion. Coloured  berries  also  readily  attract  the  attention 
of  birds  and  beasts,  which  feed  upon  them,  spread  their 
manured  seeds  abroad,  thus  giving  trees  and  shrubs 
possessing  such  berries  a  greater  chance  in  the  struggle 
for  existence. 

With  profound  analytic  and  synthetic  skill,  Mr.  Darwin 
investigates  the  cell-making  instinct  of  the  hive-bee.  His 
method  of  dealing  with  it  is  representative.  He  falls  back 
from  the  more  perfectly  to  the  less  perfectly  developed 
instinct — from  the  hive-bee  to  the  humble  bee,  which 
uses  its  own  cocoon  as  a  comb,  and  to  classes  of  bees  of 
intermediate  skill,  endeavouring  to  show  how  the  passage 
might  be  gradually  made  from  the  lowest  to  the  highest. 
The  saving  of  wax  is  the  most  important  point  in  the 
economy  of  bees.  Twelve  to  fifteen  pounds  of  dry  sugar 
are  said  to  be  needed  for  the  secretion  of  a  single  pound 
of  wax.  The  quantities  of  nectar  necessary  for  the  wax 
must  therefore  be  vast ;  and  every  improvement  of  construc- 
tive instinct  which  results  in  the  saving  of  wax  is  a  direct 
profit  to  the  insect's  life.  The  time  that  would  otherwise 
be  devoted  to  the  making  of  wax,  is  now  devoted  to  the 
gathering  and  storing  of  honey  for  winter  food.  Mr.  Darwin 
passes  from  the  humble  bee  with  its  rude  cells,  through 
the  Melipona  with  its  more  artistic  cells,  to  the  hive-bee 
with  its  astonishing  architecture.  The  bees  place  them- 
selves at  equal  distances  apart  upon  the  wax,  sweep  and 
excavate  equal  spheres  round  the  selected  points.  The 
spheres  intersect,  and  the  planes  of  intersection  are  built 
up  with  thin  laminae.  Hexagonal  c^lls  are  thus  formed. 


TUB   BELFAST   ADDRESS.  513 

This  mode  of  treating  such  questions  is,  as  I  have  said,  re- 
presentative. The  expositor  habitually  retires  from  the 
more  perfect  and  complex,  to  the  less  perfect  and  simple, 
and  carries  you  -with  him  through  stages  of  perfecting — adds 
increment  to  increment  of  infinitesimal  change,  and  in 
this  way  gradually  breaks  down  your  reluctance  to  admit 
lhat  the  exquisite  climax  of  the  whole  could  be  a  result  of 
natural  selection. 

Mr.  Darwin  shirks  no  difficulty ;  and,  saturated  as  the 
subject  was  with  his  own  thought,  he  must  have  known, 
better  than  his  critics,  the  weakness  as  well  as  the  strength 
of  his  theory.  This  of  course  would  be  of  little  avail  were 
his  object  a  temporary  dialectic  victory,  instead  of  the 
establishment  of  a  truth  which  he  means  to  be  everlast- 
ing. But  he  takes  no  pains  to  disguise  the  weakness  he 
has  discerned ;  nay,  he  takes  every  pains  to  bring  it  into 
the  strongest  light.  His  vast  resources  enable  him  to  cope 
with  objections  started  by  himself  and  others,  so  as  to 
leave  the  final  impression  upon  the  reader's  mind  that,  if 
they  be  not  completely  answered,  they  certainly  are  not 
fatal.  Their  negative  force  being  thus  destroyed,  you  are 
free  to  be  influenced  by  the  vast  positive  mass  of  evidence 
he  is  able  to  bring  before  you.  This  largeness  of  know- 
ledge, and  readiness  of  resource,  render  Mr.  Darwin  the 
most  terrible  of  antagonists.  Accomplished  naturalists 
have  levelled  heavy  and  sustained  criticisms  against  him — 
not  always  with  the  view  of  fairly  weighing  his  theory,  but 
with  the  express  intention  of  exposing  its  weak  points 
only.  This  does  not  irritate  him.  He  treats  every  ob- 
jection with  a  soberness  and  thoroughness,  which  even 
Bishop  Butler  might  be  proud  to  imitate,  surrounding 
each  fact  with  its  appropriate  detail,  placing  it  in  its 
proper  relations,  and  usually  giving  it  a  significance 
which,  as  long  as  it  was  kept  isolated,  failed  to  appear. 
This  is  done  without  a  trace  of  ill- temper.  He  moves 


514  FRAGMENTS   OF   SCIENCE. 

over  the  subject  with  the  passionless  strength  of  a  glacier ; 
and  the  grinding  of  the  rocks  is  not  always  without  a 
counterpart  in  the  logical  pulverisation  of  the  objector. 
But  though  in  handling  this  mighty  theme  all  passion  has 
been  stilled,  there  is  an  emotion  of  the  intellect,  incident 
to  the  discernment  of  new  truth,  which  often  colours  and 
warms  the  pages  of  Mr.  Darwin.  His  success  has  beet) 
great ;  and  this  implies  not  only  the  solidity  of  his  work, 
but  the  preparedness  of  the  public  mind  for  such  a  revela- 
tion. On  this  head  a  remark  of  Agassiz  impressed  me 
more  than  anything  else.  Sprung  from  a  race  of  theolo- 
gians, this  celebrated  man  combated  to  the  last  the  theory 
of  natural  selection.  One  of  the  many  times  I  had  the 
pleasure  of  meeting  him  in  the  United  States  was  at  Mr. 
Winthrop's  beautiful  residence  at  Brookline,  near  Boston. 
Eising  from  luncheon,  we  all  halted  as  if  by  common 
consent  in  front  of  a  window,  and  continued  there  a  dis- 
cussion which  had  been  started  at  table.  The  maple  was 
in  its  autumn  glory ;  and  the  exquisite  beauty  of  the  scene 
outside  seemed,  in  my  case,  to  interpenetrate  without  dis- 
turbance the  intellectual  action.  Earnestly,  almost  sadly, 
Agassiz  turned,  and  said  to  the  gentlemen  standing  round, 
'I  confess  that  I  was  not  prepared  to  see  this  theory 
received  as  it  has  been  by  the  best  intellects  of  our  time. 
Its  success  is  greater  than  I  could  have  thought  possible.' 

In  our  day  grand  generalisations  have  been  reached. 
The  theory  of  the  origin  of  species  is  but  one  of  them. 
Another,  of  still  wider  grasp  and  more  radical  significance, 
is  the  doctrine  of  the  Conservation  of  Energy,  the  ulti- 
mate philosophical  issues  of  which  are  as  yet  but  dimly 
seen — that  doctrine  which  '  binds  nature  fast  in  fate '  to 
an  extent  not  hitherto  recognised,  exacting  from  every 
antecedent  its  equivalent  consequent,  from  every  conse- 
quent its  equivalent  antecedent,  and  bringing  vital  as  well 


THE   BELFAST  ADDRESS.  615 

ts  physical  phenomena  under  the  dominion  of  that  law  of 
causal  connection  which,  so  far  as  the  human  understand- 
ing has  yet  pierced,  asserts  itself  everywhere  in  nature. 
Long  in  advance  of  all  definite  experiment  upon  the 
subject,  the  constancy  and  indestructibility  of  matter  had 
been  affirmed  ;  and  all  subsequent  experience  justified  the 
affirmation.  Mayer  extended  the  attribute  of  indestructi- 
bility to  force,  applying  it  in  the  first  instance  to  inorganic, 
and  afterwards,  with  profound  insight,  to  organic  nature. 
The  vegetable  world,  though  drawing  almost  all  its  nutri- 
ment from  invisible  sources,  was  proved  incompetent  to 
generate  anew  either  matter  or  force.  Its  matter  is  for 
the  most  part  transmuted  gas ;  its  force  transformed  solar 
force.  The  animal  world  was  proved  to  be  equally  un- 
creative,  all  its  motive  energies  being  referred  to  the 
combustion  of  its  food.  The  activity  of  each  animal,  as  a 
whole,  was  proved  to  be  the  transferred  activity  of  its  mole- 
cules. The  muscles  were  shown  to  be  stores  of  mechanical 
energy,  potential  until  unlocked  by  the  nerves,  and  then 
resulting  in  muscular  contractions.  The  speed  at  which 
messages  fly  to  and  fro  along  the  nerves  was  determined, 
and  found  to  be,  not  as  had  been  previously  supposed, 
equal  to  that  of  light  or  electricity,  but  less  than  the  speed 
of  sound — less  even  than  that  of  a  flying  eagle. 

This  was  the  work  of  the  physicist :  then  came  the  con- 
quests of  the  comparative  anatomist  and  physiologist,  re- 
vealing the  structure  of  every  animal,  and  the  function  of 
every  organ  in  the  whole  biological  series,  from  the  lowest 
zoophyte  up  to  man.  The  nervous  system  had  been  made 
the  object  of  profound  and  continued  study,  the  wonderful 
and,  at  bottom,  entirely  mysterious  controlling  power 
which  it  exercises  over  the  whole  organism,  physical  and 
mental,  being  recognised  more  and  more.  Thought 
could  not  be  kept  back  from  a  subject  so  profoundly  sug- 
gestive. Besides  the  physical  life  dealt  with  by  Mr. 


51«  FRAGMENTS   QF   SCIENCE. 

Darwin,  there  is  a  psychical  life  presenting  similar  grada- 
tions, and  asking  equally  for  a  solution.  How  are  the 
different  grades  and  orders  of  Mind  to  be  accounted  for  ? 
What  is  the  principle  of  growth  of  that  mysterious  power 
which  on  our  planet  culminates  in  Eeason  ?  These  are 
questions  which,  though  not  thrusting  themselves  so 
forcibly  upon  the  attention  of  the  general  public,  had  not 
only  occupied  many  reflecting  minds,  but  had  been  for- 
mally broached  by  one  of  them  before  the  '  Origin  of 
Species '  appeared. 

With  the  mass  of  materials  furnished  by  the  physicist 
and  physiologist  in  his  hands,  Mr.  Herbert  Spencer, 
twenty  years  ago,  sought  to  graft  upon  this  basis  a  system 
of  psychology ;  and  two  years  ago  a  second  and  greatly 
amplified  edition  of  his  work  appeared.  Those  who  have 
occupied  themselves  with  the  beautiful  experiments  of 
Plateau  will  remember  that  when  two  spherules  of  olive- 
oil,  suspended  in  a  mixture  of  alcohol  and  water  of  the 
same  density  as  the  oil,  are  brought  together,  they  do  not 
immediately  unite.  Something  like  a  pellicle  appears  to 
be  formed  around  the  drops,  the  rupture  of  which  is  imme- 
diately followed  by  the  coalescence  of  the  globules  into 
one.  There  are  organisms  whose  vital  actions  are  almost 
as  purely  physical  as  that  of  these  drops  of  oil.  They  come 
into  contact  and  fuse  themselves  thus  together.  From 
such  organisms  to  others  a  shade  higher,  from  these  to 
others  a  shade  higher  still,  and  on  through  an  ever  ascend- 
ing series,  Mr.  Spencer  conducts  his  argument.  There 
are  two  obvious  factors  to  be  here  taken  into  account — 
the  creature  and  the  medium  in  which  it  lives,  or,  as  it  is 
often  expressed,  the  organism  and  its  environment.  Mr. 
Spencer's  fundamental  principle  is,  that  between  these 
two  factors  there  is  incessant  interaction.  The  organism 
is  played  upon  by  the  environment,  and  is  modified  to 
meet  the  requirements  of  the  environment.  Life  he  defines 


THE  BELFAST  ADDEESS.  617 

to  be  'a  continuous  adjustment  of  internal  relations  to  ex- 
ternal relations.' 

In  the  lowest  organisms  we  have  a  kind  of  tactual  sense 
diffused  over  the  entire  body  ;  then,  through  impressions 
from  without  and  their  corresponding  adjustments,  special 
portions  of  the  surface  become  more  responsive  to  stimuli 
than  others.  The  senses  are  nascent,  the  basis  of  all  of  them 
being  that  simple  tactual  sense  which  the  sage  Democritus 
recognised  2,300  years  ago  as  their  common  progenitor.  The 
action  of  light,  in  the  first  instance,  appears  to  be  a  mere  dis- 
turbance of  the  chemical  processes  in  the  animal  organism, 
similar  to  that  which  occurs  in  the  leaves  of  plants.  By  de- 
grees the  action  becomes  localised  in  a  few  pigment-cells, 
more  sensitive  to  light  than  the  surrounding  tissue.  The 
eye  is  incipient.  At  first  it  is  merely  capable  of  revealing 
differences  of  light  and  shade  produced  by  bodies  close 
at  hand.  Followed,  as  the  interception  of  the  light  is,  in 
almost  all  cases,  by  the  contact  of  the  closely  adjacent 
opaque  body,  sight  in  this  condition  becomes  a  kind  of 
*  anticipatory  touch.'  The  adjustment  continues  ;  a  slight 
bulging  out  of  the  epidermis  over  the  pigment-granules 
supervenes.  A  lens  is  incipient,  and,  through  the  opera- 
tion of  infinite  adjustments,  at  length  reaches  the  perfec- 
tion that  it  displays  in  the  hawk  and  eagle.  So  of  the 
other  senses ;  they  are  special  differentiations  of  a  tissue 
which  was  originally  vaguely  sensitive  all  over. 

With  the  development  of  the  senses,  the  adjustments 
between  the  organism  and  its  environment  gradually  ex- 
tend in  space,  a  multiplication  of  experiences  and  a  corre- 
sponding modification  of  conduct  being  the  result.  The 
adjustments  also  extend  in  time,  covering  continually 
greater  intervals.  Along  with  this  extension  in  space  and 
time  the  adjustments  also  increase  in  speciality  and  com- 
plexity, passing  through  the  various  grades  of  brute  life, 
and  prolonging  themselves  into  the  domain  of  reason. 


618  FRAGMENTS    OF   SCIENCE. 

Very  striking  are  Mr.  Spencer's  remarks  regarding  the  in- 
fluence of  the  sense  of  touch  upon  the  development  of 
intelligence.  This  is,  so  to  say,  the  mother-tongue  of  all 
the  senses,  into  which  they  must  be  translated  to  be  of 
service  to  the  organism.  Hence  its  importance.  The 
parrot  is  the  most  intelligent  of  birds,  and  its  tactual  power 
is  also  greatest.  From  this  sense  it  gets  knowledge,  unat- 
tainable by  birds  which  cannot  employ  their  feet  as  hands. 
The  elephant  is  the  most  sagacious  of  quadrupeds — its 
tactual  range  and  skill,  and  the  consequent  multiplication 
of  experiences,  which  it  owes  to  its  wonderfully  adaptable 
trunk,  being  the  basis  of  its  sagacity.  Feline  animals,  for 
a  similar  cause,  are  more  sagacious  than  hoofed  animals, 
— atonement  being  to  some  extent  made  in  the  case  of 
the  horse,  by  the  possession  of  sensitive  prehensile  lips. 
In  the  Primates  the  evolution  of  intellect  and  the  evolu- 
tion of  tactual  appendages  go  hand  in  hand.  In  the  most 
intelligent  anthropoid  apes  we  find  the  tactual  range  and 
delicacy  greatly  augmented,  new  avenues  of  knowledge 
being  thus  opened  to  the  animal.  Man  crowns  the  edifice 
here,  not  only  in  virtue  of  his  own  manipulatory  power, 
but  through  the  enormous  extension  of  his  range  of  ex- 
perience, by  the  invention  of  instruments  of  precision, 
which  serve  as  supplemental  senses  and  supplemental  limbs 
The  xeciprocal  action  of  these  is  finely  described  and  illus- 
trated. That  chastened  intellectual  emotion  to  which  I 
have  referred  in  connection  with  Mr.  Darwin,  is  not  absent 
in  Mr.  Spencer.  His  illustrations  possess  at  times  ex- 
ceeding vividness  and  force ;  and  from  his  style  on  such 
occasions  it  is  to  be  inferred,  that  the  ganglia  of  this 
Apostle  of  the  Understanding  are  sometimes  the  seat  of  a 
nascent  poetic  thrill. 

It  is  a  fact  of  supreme  importance  that  actions,  the 
performance  of  which  at  first  requires  even  painful  effort 
and  deliberation,  may,  by  habit,  be  rendered  automatic. 


THE    BELFAST   ADDRESS.  619 

Witness  the  slow  learning  of  its  letters  by  a  child,  and 
the  subsequent  facility  of  reading  in  a  man,  when  each 
group  of  letters  which  forms  a  word  is  instantly,  and  with- 
out effort,  fused  to  a  single  perception.  Instance  the 
billiard  player,  whose  muscles  of  hand  and  eye,  when  he 
reaches  the  perfection  of  his  art,  are  unconsciously  co-ordi- 
nated. Instance  the  musician,  who,  by  practice,  is  en- 
abled to  fuse  a  multitude  of  arrangements,  auditory, 
tactual,  and  muscular,  into  a  process  of  automatic  mani- 
pulation. Combining  such  facts  with  the  doctrine  of 
hereditary  transmission,  we  reach  a  theory  of  Instinct. 
A  chick,  after  coming  out  of  the  egg,  balances  itself 
correctly,  runs  about,  picks  up  food,  thus  showing  that  it 
possesses  a  power  of  directing  its  movements  to  definite 
ends.  How  did  the  chick  learn  this  very  complex  co- 
ordination of  eye,  muscles,  and  beak?  It  has  not  been 
individually  taught ;  its  personal  experience  is  nil ;  but  it 
has  the  benefit  of  ancestral  experience.  In  its  inherited 
organisation  are  registered  the  powers  which  it  displays 
at  birth.  So  also  as  regards  the  instinct  of  the  hive-bee, 
already  referred  to.  The  distance  at  which  the  insects 
stand  apart  when  they  sweep  their  hemispheres  and  build 
their  cells  is  *  organically  remembered.'  Man  also  carries 
with  him  the  physical  texture  of  his  ancestry,  as  well  as 
the  inherited  intellect  bound  up  with  it.  The  defects  of 
intelligence  during  infancy  and  youth  are  probably  less 
due  to  a  lack  of  individual  experience,  than  to  the  fact 
that  in  early  life  the  cerebral  organisation  is  still  incom- 
plete. The  period  necessary  for  completion  varies  with 
the  race,  and  with  the  individual.  As  a  round  shot  out- 
strips a  rifled  bolt  on  quitting  the  muzzle  of  the  gun,  so 
the  lower  race,  in  childhood,  may  outstrip  the  higher.  But 
the  higher  eventually  overtakes  the  lower,  and  surpasses 
it  in  range.  As  regards  individuals,  we  do  not  always 
find  the  precocity  of  youth  prolonged  to  mental  power  in 


520  FRAGMENTS   OF    SCIENCE. 

maturity ;  while  the  dulness  of  boyhood  is  sometimes 
strikingly  contrasted  with  the  intellectual  energy  of  after 
years.  Newton,  when  a  boy,  was  weakly,  and  he  showed 
no  particular  aptitude  at  school ;  but  in  his  eighteenth 
year  he  went  to  Cambridge,  and  soon  afterwards  astonished 
his  teachers  by  his  power  of  dealing  with  geometrical 
problems.  During  his  quiet  youth,  his  brain  was  slowly 
preparing  itself  to  be  the  organ  of  those  energies  which  he 
subsequently  displayed. 

By  myriad  blows  (to  use  a  Lucretian  phrase)  the 
image  and  superscription  of  the  external  world  are  stamped 
as  states  of  consciousness  upon  the  organism,  the  depth 
of  the  impression  depending  upon  the  number  of  the  blows. 
When  two  or  more  phenomena  occur  in  the  environment 
invariably  together,  they  are  stamped  to  the  same  depth 
or  to  the  same  relief,  and  indissolubly  connected.  And 
here  we  come  to  the  threshold  of  a  great  question.  See- 
ing that  he  could  in  no  way  rid  himself  of  the  conscious- 
ness of  Space  and  Time,  Kant  assumed  them  to  be  neces- 
sary '  forms  of  intuition,'  the  moulds  and  shapes  into 
which  our  intuitions  are  thrown,  belonging  to  ourselves, 
and  without  objective  existence.  With  unexpected  power 
and  success  Mr.  Spencer  brings  the  hereditary  experi- 
ence theory,  as  he  holds  it,  to  bear  upon  this  question. 
1  If  there  exist  certain  external  relations  which  are  experi- 
enced by  all  organisms  at  all  instants  of  their  waking 
lives — relations  which  are  absolutely  constant  and  uni- 
versal— there  will  be  established  answering  internal 
relations,  that  are  absolutely  constant  and  universal. 
Such  relations  we  have  in  those  of  Space  and  Time.  As 
the  substratum  of  all  other  relations  of  the  Non-Ego,  they 
must  be  responded  to  by  conceptions  that  are  the  sub- 
strata of  all  other  relations  in  the  Ego.  Being  the  con- 
stant and  infinitely  repeated  elements  of  thought,  they 
must  become  the  automatic  elements  of  thought — the  ele- 


THE    BELFAST   ADDRESS.  521 

ments  of  thought  which  it  is  impossible  to  get  rid  of — the 
"  forms  of  intuition." ' 

Throughout  this  application  and  extension  of  Hartley's 
and  Mill's  '  Law  of  Inseparable  Association,'  Mr.  Spencer 
stands  upon  his  own  ground,  invoking,  instead  of  the  experi- 
ences of  the  individual,  the  registered  experiences  of  the 
race.  His  overthrow  of  the  restriction  of  experience  to  the 
individual  is,  I  think,  complete.  That  restriction  ignores 
the  power  of  organising  experience,  furnished  at  the  out- 
set to  each  individual ;  it  ignores  the  different  degrees  of 
this  power  possessed  by  different  races,  and  by  different 
individuals  of  the  same  race.  Were  there  not  in  the 
human  brain  a  potency  antecedent  to  all  experience,  a  dog 
or  a  cat  ought  to  be  as  capable  of  education  as  a  man. 
These  predetermined  internal  relations  are  independent  of 
the  experiences  of  the  individual.  The  human  brain  is 
the  '  organised  register  of  infinitely  numerous  experiences 
received  during  the  evolution  of  life,  or  rather  during  the 
evolution  of  that  series  of  organisms  through  which  the 
human  organism  has  been  reached.  The  effects  of  the 
most  uniform  and  frequent  of  these  experiences  have  been 
successively  bequeathed,  principal  and  interest,  and  have 
slowly  mounted  to  that  high  intelligence  which  lies  latent 
in  the  brain  of  the  infant.  Thus  it  happens  that  the 
European  inherits  from  twenty  to  thirty  cubic  inches 
more  of  brain  than  the  Papuan.  Thus  it  happens  that 
faculties,  as  of  music,  which  scarcely  exist  in  some 
inferior  races,  become  congenital  in  superior  ones.  Thus 
it  happens  that  out  of  savages  unable  to  count  up  to  the 
number  of  their  fingers,  and  speaking  a  language  con- 
taining only  nouns  and  verbs,  arise  at  length  our  Newtons 
and  Shakspeares.' 

At  the  outset  of  this  Address  it  was  stated  that  physi- 
cal theories  which  lie  beyond  experience  are  derived  by  a 
process  of  abstraction  from  experience.  It  is  instructive 


r>±J  FRAGMENTS   OP   SCIENCE. 

to  note  from  this  point  of  view  the  successive  introduction 
of  new  conceptions.  The  idea  of  the  attraction  of  gravi- 
tation was  preceded  by  the  observation  of  the  attraction 
of  iron  by  a  magnet,  and  of  light  bodies  by  rubbed 
amber.  The  polarity  of  magnetism  and  electricity  also 
appealed  to  the  senses.  It  thus  became  the  substratum  of 
the  conception  that  atoms  and  molecules  are  endowed  witli 
attractive  and  repellent  poles,  by  the  play  of  which  de- 
finite forms  of  crystalline  architecture  are  produced. 
Thus  molecular  force  becomes  structural.1  It  required  no 
great  boldness  of  thought  to  extend  its  play  into  organic 
nature,  and  to  recognise  in  molecular  force  the  agency  by 
which  both  plants  and  animals  are  built  up.  In  this  way, 
out  of  experience  arise  conceptions  which  are  wholly  ultra- 
experiential.  None  of  the  atomists  of  antiquity  had  any 
notion  of  this  play  of  molecular  polar  force,  but  they  had 
experience  of  gravity  as  manifested  by  falling  bodies. 
Abstracting  from  this,  they  permitted  their  atoms  to  fall 
eternally  through  empty  space.  Democritus  assumed  that 
the  larger  atoms  moved  more  rapidly  than  the  smaller 
ones,  which  they  therefore  could  overtake,  and  with  which 
they  could  combine.  Epicurus,  holding  that  empty  space 
could  offer  no  resistance  to  motion,  ascribed  to  all  the 
atoms  the  same  velocity ;  but  he  seems  to  have  over- 
looked the  consequence  that  under  such  circumstances  the 
atoms  could  never  combine.  Lucretius  cut  the  knot  by 
quitting  the  domain  of  physics  altogether,  and  causing 
the  atoms  to  move  together  by  a  kind  of  volition. 

Was  the  instinct  utterly  at  fault  which  caused 
Lucretius  thus  to  swerve  from  his  own  principles  ?  Di- 
minishing gradually  the  number  of  progenitors,  Mr. 
Darwin  comes  at  length  to  one  '  primordial  form;'  but  he 
does  not  say,  so  far  as  I  remember,  how  he  supposes  this 

1  Soe  Art.  VIII.,  Part  II.,  of  this  relume,  or  '  Leof.ires  on  Light,'  III. 


THE  BELFAST  ADDEESS.  523 

form  to  have  been  introduced.  He  quotes  with  satis- 
faction the  words  of  a  celebrated  author  and  divine 
who  had  '  gradually  learnt  to  see  that  it  was  just  as  noble 
a  conception  of  the  Deity  to  believe  He  created  a  few 
original  forms,  capable  of  self-development  into  other  and 
needful  forms,  as  to  believe  He  required  a  fresh  act  of 
creation  to  supply  the  voids  caused  by  the  action  of  His 
laws.'  What  Mr.  Darwin  thinks  of  this  view  of  the  intro- 
duction of  life  I  do  not  know.  But  the  anthropomorphism, 
which  it  seemed  his  object  to  set  aside,  is  as  firmly  asso 
elated  with  the  creation  of  a  few  forms  as  with  the  creation 
of  a  multitude.  We  need  clearness  and  thoroughness  here. 
Two  courses  and  two  only  are  possible.  Either  let  us 
open  our  doors  freely  to  the  conception  of  creative  acts, 
or,  abandoning  them,  let  us  radically  change  our  notions 
of  Matter.  If  we  look  at  matter  as  pictured  by  Democri- 
tus,  and  as  defined  for  generations  in  our  scientific  text- 
books, the  notion  of  conscious  life  corning  out  of  it,  cannot 
be  formed  by  the  mind.  The  argument  placed  in  the  mouth 
of  Bishop  Butler  suffices,  in  my  opinion,  to  crush  all  such 
materialism  as  this.  Those,  however,  who  framed  these 
definitions  of  matter  were  but  partial  students.  They  were 
not  biologists,  but  mathematicians,  whose  labours  referred 
only  to  such  accidents  and  properties  of  matter  as  could  be 
expressed  in  their  formulae.  Their  science  was  mechanical 
science,  not  the  science  of  life.  With  matter  in  its 
wholeness  they  never  dealt ;  and,  denuded  by  their  imper- 
fect definitions,  '  the  gentle  mother  of  all '  became  the 
object  of  her  children's  dread.  Let  us  reverently,  but 
honestly,  look  the  question  in  the  face.  Divorced  from 
matter,  where  is  life  ?  Whatever  our  faith  may  say,  our 
knowledge  shows  them  to  be  indissolubly  joined.  Every 
meal  we  eat,  and  every  cup  we  drink,  illustrates  the 
mysterious  control  of  Mind  by  Matter. 

On  tracing  the  line  of  life  backwards,  we  see  it  ap- 


524  FRAGMENTS   OP  SCIENCE. 

preaching  more  and  more  to  what  we  call  the  purely  physi- 
cal condition.  We  come  at  length  to  those  organisms  which 
I  have  compared  to  drops  of  oil,  suspended  in  a  mixture  of 
alcohol  and  water.  We  reach  the  protogenes  of  Haeckel, 
in  which  we  have  '  a  type  distinguishable  from  a  fragment 
of  albumen  only  by  its  finely  granular  character.'  Can 
we  pause  here  ?  We  break  a  magnet  and  find  two  poles 
in  each  of  its  fragments.  We  continue  the  process  of 
breaking;  but,  however  small  the  parts,  each  carries  with 
it,  though  enfeebled,  the  polarity  of  the  whole.  And 
when  we  can  break  no  longer,  we  prolong  the  intellectual 
vision  to  the  polar  molecules.  Are  we  not  urged  to  do 
something  similar  in  the  case  of  life  ?  Is  there  not  a 
temptation  to  close  to  some  extent  with  Lucretius,  when 
he  affirms  that  '  Nature  is  seen  to  do  all  things  sponta- 
neously of  herself  without  the  meddling  of  the  gods  ? '  or 
with  Bruno,  when  he  declares  that  Matter  is  not  '  that 
mere  empty  capacity  which  philosophers  have  pictured 
her  to  be,  but  the  universal  mother  who  brings  forth  all 
things  as  the  fruit  of  her  own  womb  ? '  Believing  as  I 
do,  in  the  continuity  of  nature,  I  cannot  stop  abruptly 
where  our  microscopes  cease  to  be  of  use.  Here  the 
vision  of  the  mind  authoritatively  supplements  the  vision 
of  the  eye.  By  an  intellectual  necessity  I  cross  the 
boundary  of  the  experimental  evidence,1  and  discern  in 
that  Matter  which  we,  in  our  ignorance  of  its  latent 
powers,  and  notwithstanding  our  professed  reverence  for 
its  Creator,  have  hitherto  covered  with  opprobrium,  the 
promise  and  potency  of  all  terrestrial  Life. 

If  you  ask  me  whether  there  exists  the  least  evidence 
to  prove  that  any  form  of  life  can  be  developed  out  of 
matter,  without  demonstrable  antecedent  life,  my  reply  is 


1  This  mode  of  procedure  was  noc  invented  in  Belfast.     See  first  para- 
graph, Art.  III.,  Part  I.,  of  this  volume ;  written  in  1856. 


THE  BELFAST  ADDRESS.  626 

that  evidence  considered  perfectly  conclusive  by  many  has 
been  adduced ;  and  that  were  some  of  us  who  have  pon- 
dered this  question  to  follow  a  very  common  example,  and 
accept  testimony  because  it  falls  in  with  our  belief,  we 
also  should  eagerly  close  with  the  evidence  referred  to. 
But  there  is  in  the  true  man  of  science  a  desire  stronger 
than  the  wish  to  have  his  beliefs  upheld ;  namely,  the 
desire  to  have  them  true.  And  this  stronger  wish  causes 
him  to  reject  the  most  plausible  support,  if  he  has  reason 
to  suspect  that  it  is  vitiated  by  error.  Those  to  whom  I 
refer  as  having  studied  this  question,  believing  the  evidence 
offered  in  favour  of  '  spontaneous  generation '  to  be  thus 
vitiated,  cannot  accept  it.  They  know  full  well  that  the 
chemist  now  prepares  from  inorganic  matter  a  vast  array 
of  substances,  which  were  some  time  ago  regarded  as  the 
sole  products  of  vitality.  They  are  intimately  acquainted 
with  the  structural  power  of  matter,  as  evidenced  in  the 
phenomena  of  crystallisation.  They  can  justify  scien- 
tifically their  belief  in  its  potency,  under  the  proper 
conditions,  to  produce  organisms.  But,  in  reply  to  your 
question,  they  will  frankly  admit  their  inability  to  point 
to  any  satisfactory  experimental  proof  that  life  can  be  deve- 
loped, save  from  demonstrable  antecedent  life.  As  already 
indicated,  they  draw  the  line  from  the  highest  organisms 
through  lower  ones  down  to  the  lowest,  and  it  is  the  pro- 
longation of  this  line  by  the  intellect,  beyond  the  range 
of  the  senses,  that  leads  them  to  the  conclusion  which 
Bruno  so  boldly  enunciated.1 

The  '  materialism '  here  professed  may  be  vastly  dif- 
ferent from  what  you  suppose,  and  I  therefore  crave  your 
gracious  patience  to  the  end.  '  The  question  of  an 
external  world,'  says  J.  S.  Mill,  'is  the  great  battle- 
ground of  metaphysics.' 2  Mr.  Mill  himself  reduces  ex- 

1  Bruno  was  a  '  Pantheist,'  not  an  'Atheist'  or  a  'Materialist.' 
•  'Examination  of  Hamilton,'  p.  154. 


52(5  FRAGMENTS   OF   SCIENCE. 

ternal  phenomena  to  *  possibilities  of  sensation.'  Kant,  as 
we  have  seen,  made  time  and  space  '  forms '  of  our  own  in- 
tuitions. Fichte,  having  first  by  the  inexorable  logic  of 
his  understanding  proved  himself  to  be  a  mere  link  in 
that  chain  of  eternal  causation  which  holds  so  rigidly  in 
nature,  violently  broke  the  chain  by  making  nature,  and 
all  that  it  inherits,  an  apparition  of  the  mind.1  And  it  is 
by  no  means  easy  to  combat  such  notions.  For  when  I  say 
I  see  you,  and  that  I  have  not  the  least  doubt  about  it,  the 
obvious  reply  is,  that  what  I  am  really  conscious  of  is  an 
affection  of  my  own  retina.  And  if  I  urge  that  I  can 
check  my  sight  of  you  by  touching  you,  the  retort  would 
be  that  I  am  equally  transgressing  the  limits  of  fact ;  for 
what  I  am  really  conscious  of  is,  not  that  you  are  there, 
but  that  the  nerves  of  my  hand  have  undergone  a  change. 
All  we  hear,  and  see,  and  touch,  and  taste,  and  smell,  are, 
it  would  be  urged,  mere  variations  of  our  own  condition, 
beyond  which,  even  to  the  extent  of  a  hair's  breadth,  we 
cannot  go.  That  anything  answering  to  our  impressions 
exists  outside  of  ourselves  is  not  a  fact,  but  an  inference, 
to  which  all  validity  would  be  denied  by  an  idealist  like 
Berkeley,  or  by  a  sceptic  like  Hume.  Mr.  Spencer  takes 
another  line.  With  him,  as  with  the  uneducated  man, 
there  is  no  doubt  or  question  as  to  the  existence  of  an  ex- 
ternal world.  But  he  differs  from  the  uneducated,  who 
think  that  the  world  really  is  what  consciousness  represents 
it  to  be.  Our  states  of  consciousness  are  mere  symbols  of 
an  outside  entity  which  produces  them  and  determines  the 
order  of  their  succession,  but  the  real  nature  of  which  we 
can  never  know.2  In  fact,  the  whole  process  of  evolution  is 

1  '  JBestimmung  des  Menschen. 

2  In  a  paper,  at  once  popular  and  profound,  entitled  '  Keeent  Progress 
in  the  Theory  of  Vision,'  contained  in  the  volume  of  lectures  by  Ilelmholtz, 
published  by  Longmans,  this  symbolism  of  our  states  of  consciousness  is 
also  iwelt  upon.     The  impressions  of  sense  are  the  mere  signs  of  external 


THE   BELFAST  ADDRESS.  627 

the  manifestation  of  a  Power  absolutely  inscrutable  to  the 
intellect  of  man.  As  little  in  our  day  as  in  the  days  of 
Job  can  man  by  searching  find  this  Power  out.  Con- 
sidered fundamentally,  then,  it  is  by  the  operation  of  an 
insoluble  mystery  that  life  on  earth  is  evolved,  species 
differentiated,  and  mind  unfolded  from  their  prepotent 
elements  in  the  immeasurable  past.  There  is,  you  will 
observe,  no  very  rank  materialism  here. 

The  strength  of  the  doctrine  of  evolution  consists,  not 
in  an  experimental  demonstration  (for  the  subject  is  hardly 
accessible  to  this  mode  of  proof),  but  in  its  general 
harmony  with  scientific  thought.  From  contrast,  more- 
over, it  derives  enormous  relative  strength.  On  the  one 
side  we  have  a  theory  (if  it  could  with  any  propriety  be 
so  called)  derived,  as  were  the  theories  referred  to  at  the 
beginning  of  this  Address,  not  from  the  study  of  nature, 
but  from  the  observation  of  men — a  theory  which  converts 
the  Power  whose  garment  is  seen  in  the  visible  universe 
into  an  Artificer,  fashioned  after  the  human  model,  and 
acting  by  broken  efforts  as  man  is  seen  to  act.  On  the 
other  side  we  have  the  conception  that  all  we  see  around 
us,  and  all  we  feel  within  us — the  phenomena  of  physical 
nature  as  well  as  those  of  the  human  mind — have  their 
unsearchable  roots  in  a  cosmical  life,  if  I  dare  apply  the 
term,  an  infinitesimal  span  of  which  is  offered  to  the  in- 
vestigation of  man.  And  even  this  span  is  only  knowable 

things.  In  this  paper  Helmholtz  contends  strongly  against  the  view  that 
the  consciousness  of  space  is  inborn ;  and  he  evidently  doubts  the  power  of 
the  chick  to  pick  up  grains  of  corn  without  preliminary  lessons.  On  this 
point,  he  says,  further  experiments  are  needed.  Such  experiments  have 
been  since  made  by  Mr.  Spalding,  aided,  I  believe,  in  some  of  his  observa- 
tions by  the  accomplished  and  deeply  lamented  Lady  Amberly  ;  and  they 
seem  to  prove  conclusively  that  the  chick  does  not  need  a  single  moment's 
tuition  to  enable  it  to  stand,  run,  govern  the  muscles  of  its  eyes,  and  peck. 
Helmholtz,  however,  is  contending  against  the  notion  of  pre-established 
harmony ;  and  I  am  not  aware  of  his  views  as  to  the  organisation  of  e»- 
p  -ricnces  cf  race  or  breed. 


528  FKAGMENTS   OF   SCIENCE. 

in  part.  We  can  trace  the  development  of  a  nervous 
system,  and  correlate  with  it  the  parallel  phenomena  of 
sensation  and  thought.  We  see  with  undoubting  certainty 
that  they  go  hand  in  hand.  But  we  try  to  soar  in  a 
vacuum  the  moment  we  seek  to  comprehend  the  connection 
between  them.  An  Archimedean  fulcrum  is  here  required 
which  the  human  mind  cannot  command ;  and  the  effort 
to  solve  the  problem — to  borrow  a  comparison  from  an 
illustrious  friend  of  mine — is  like  the  effort  of  a  man 
trying  to  lift  himself  by  his  own  waistband.  All  that  has 
been  said  in  this  discourse  is  to  be  taken  in  connection  with 
this  fundamental  truth.  When  'nascent  senses'  are  spoken 
of,  when  '  the  differentiation  of  a  tissue  at  first  vaguely 
sensitive  all  over '  is  spoken  of,  and  when  these  processes 
are  associated  with  '  the  modification  of  an  organism  by 
its  environment,'  the  same  parallelism,  without  contact, 
or  even  approach  to  contact,  is  implied.  Man  the 
object  is  separated  by  an  impassable  gulf  from  man  the 
subject.  There  is  no  motor  energy  in  the  human  intellect 
to  carry  it,  without  logical  rupture,  from  the  one  to  the 
other. 

Further,  the  doctrine  of  evolution  derives  man,  in  his 
totality,  from  the  interaction  of  organism  and  environment 
through  countless  ages  past.  The  Human  Understanding, 
for  example, — that  faculty  which  Mr.  Spencer  has  turned 
so  skilfully  round  upon  its  own  antecedents — is  itself  a 
result  of  the  play  between  organism  and  environment 
through  cosmic  ranges  of  time.  Never,  surely,  did  pre- 
scription plead  so  irresistible  a  claim.  But  then  it  comes 
to  pass  that,  over  and  above  his  understanding,  there  are 
many  other  things  appertaining  to  man,  whose  prescriptive 
rights  are  quite  as  strong  as  those  of  the  understanding 
itself.  It  is  a  result,  for  example,  of  the  play  of  organism 
and  environment  that  sugar  is  sweet,  and  that  aloes  are 
bitter ;  that  the  smell  of  henbane  differs  from  the  perfume 


THE   BELFAST   ADDRESS.  629 

of  a  rose.  Such  facts  of  consciousness  (for  which,  by  the 
way,  no  adequate  reason  has  ever  been  rendered)  are  quite 
as  old  as  the  understanding;  and  many  other  things 
can  boast  an  equally  ancient  origin.  Mr.  Spencer  at  one 
place  refers  to  that  most  powerful  of  passions — the  amatory 
passion — as  one  which,  when  it  first  occurs,  is  antecedent 
to  all  relative  experience  whatever  ;  and  we  may  pass  its 
claim  as  being  at  least  as  ancient,  and  as  valid,  as  that  of 
the  understanding  itself.  Then  there  are  such  things  woven 
into  the  texture  of  man  as  the  feeling  of  Awe,  Keverence, 
Wonder — and  not  alone  the  sexual  love  just  referred  to,  but 
the  love  of  the  beautiful,  physical,  and  moral,  in  Nature, 
Poetry,  and  Art.  There  is  also  that  deep-set  feeling, 
which,  since  the  earliest  dawn  of  history,  and  probably 
for  ages  prior  to  all  history,  incorporated  itself  in  the 
Religions  of  the  world.  You,  who  have  escaped  from  these 
religions  into  the  high-and-dry  light  of  the  intellect,  may 
deride  them ;  but  in  so  doing  you  deride  accidents  of  form 
merely,  and  fail  to  touch  the  immovable  basis  of  the  re- 
ligious sentiment  in  the  nature  of  man.  To  yield  this 
sentiment  reasonable  satisfaction  is  the  problem  of  problems 
at  the  present  hour.  And  grotesque  in  relation  to  scien- 
tific culture  as  many  of  the  religions  of  the  world  have  been 
and  are — dangerous,  nay,  destructive,  to  the  dearest  pri- 
vileges of  freemen  as  some  of  them  undoubtedly  have 
been,  and  would,  if  they  could,  be  again — it  will  be  wise 
to  recognise  them  as  the  forms  of  a  force,  mischievous  if 
permitted  to  intrude  on  the  region  of  objective  know- 
ledge, over  which  it  holds  no  command,  but  capable  of 
adding,  in  the  region  of  poetry  and  emotion,  inward  com- 
pleteness and  dignity  to  man. 

Feeling,  I  say  again,  dates  from  as  old  an  origin  and 

as  high  a  source  as  intelligence,  and  it  equally  demands 

its  range  of  play.     The  wise  teacher  of  humanity  will  re- 

.  cognise  the  necessity  of  meeting  this  demand,  rather  than 


630  FRAGMENTS    OP   SCIENCE. 

of  resisting  it  on  account  of  errors  and  absurdities  of  form. 
What  we  should  resist,  at  all  hazards,  is  the  attempt  made 
in  the  past,  and  now  repeated,  to  found  upon  this  elemental 
bias  of  man's  nature  a  system  which  should  exercise  des- 
potic sway  over  his  intellect.  I  have  no  fear  of  such 
a  consummation.  Science  has  already  to  some  extent 
leavened  the  world  :  it  will  leaven  it  more  and  more  ;  and  I 
should  look  upon  the  mild  light  of  science  breaking  in  upon 
the  minds  of  the  youth  of  Ireland,  and  strengthening  gra- 
dually to  the  perfect  day,  as  a  surer  check  to  any  intel- 
lectual or  spiritual  tyranny  which  now  threatens  this 
island,  than  the  laws  of  princes  or  the  swords  of  emperors. 
We  fought  and  won  our  battle  even  in  the  Middle  Ages : 
should  we  doubt  the  issue  of  another  conflict  with  our 
broken  foe  ? 

The  impregnable  position  of  science  may  be  described 
in  a  few  words.  We  claim,  and  we  shall  wrest  from  theo- 
logy, the  entire  domain  of  cosmological  theory.  All 
schemes  and  systems  which  thus  infringe  upon  the  domain 
of  science  must,  in  so  far  as  they  do  this,  submit  to  its 
control,  and  relinquish  all  thought  of  controlling  it.  Act- 
ing otherwise  proved  disastrous  in  the  past,  and  it  is  simply 
fatuous  to-day.  Every  system  which  would  escape  the  fate 
of  an  organism  too  rigid  to  adjust  itself  to  its  environment, 
must  be  plastic  to  the  extent  that  the  growth  of  knowledge 
demands.  When  this  truth  has  been  thoroughly  taken 
in,  rigidity  will  be  relaxed,  exclusiveness  diminished,  things 
now  deemed  essential  will  be  dropped,  and  elements  now 
rejected  will  be  assimilated.  The  lifting  of  the  life  is  the 
essential  point ;  and  as  long  as  dogmatism,  fanaticism, 
and  intolerance  are  kept  out,  various  modes  of  leverage 
may  be  employed  to  raise  life  to  a  higher  level. 

Science  itself  not  unfrequently  derives  motive  power 
from  an  ultra-scientific  source.  Some  of  its  greatest  disco- 
veries have  been  made  under  the  stimulus  of  a  non-scientific 


THE   BELFAST  ADDRESS.  531 

ideal.  This  was  the  case  among  the  ancients,  and  it  has 
been  so  amongst  ourselves.  Mayer,  Joule,  and  Colding, 
whose  names  are  associated  with  the  greatest  of  modern 
generalisations,  were  thus  influenced.  With  his  usual  in- 
sight, Lange  at  one  place  remarks,  that  '  it  is  not  always 
the  objectively  correct  and  intelligible  that  helps  man 
most,  or  leads  most  quickly  to  the  fullest  and  truest  know- 
ledge. As  the  sliding  body  upon  the  brachystochrone 
reaches  its  end  sooner  than  by  the  straighter  road  of  the 
inclined  plane,  so,  through  the  swing  of  the  ideal,  we 
often  arrive  at  the  naked  truth  more  rapidly  than  by  the 
direct  processes  of  the  understanding.'  Whewell  speaks 
of  enthusiasm  of  temper  as  a  hindrance  to  science ;  but 
he  means  the  enthusiasm  of  weak  heads.  There  is  a 
strong  and  resolute  enthusiasm  in  which  science  finds 
an  ally ;  and  it  is  to  the  lowering  of  this  fire,  rather 
than  to  the  diminution  of  intellectual  insight,  that  the 
lessening  productiveness  of  men  of  science,  in  their 
mature  years,  is  to  be  ascribed.  Mr.  Buckle  sought  to 
detach  intellectual  achievement  from  moral  force.  He 
gravely  erred;  for  without  moral  force  to  whip  it  into 
action,  the  achievement  of  the  intellect  would  be  poor 
indeed. 

It  has  been  said  by  its  opponents  that  science  divorces 
itself  from  literature ;  but  the  statement,  like  so  many 
others,  arises  from  lack  of  knowledge.  A  glance  at  the  less 
technical  writings  of  its  leaders — of  its  Helmholtz,  its  Hux- 
ley, and  its  Du  Bois-Eeymond — would  show  what  breadth  of 
literary  culture  they  command.  Where  among  modern 
writers  can  you  find  their  superiors  in  clearness  and  vigour 
of  literary  style  ?  Science  desires  not  isolation,  but  freely 
combines  with  every  effort  towards  the  bettering  of  man's 
estate.  Single-handed,  and  supported  not  by  outward  sym- 
pathy, but  by  inward  force,  it  has  built  at  least  one  great 
wing  of  the  many-mansioned  home  which  man  in  his  to- 
25 


632  FRAGMENTS   OF   SCIENCE. 

tality  demands.  And  if  rough  walls  and  protruding  rafter- 
ends  indicate  that  on  one  side  the  edifice  is  still  incomplete, 
it  is  only  by  wise  combination  of  the  parts  required,  with 
those  already  irrevocably  built,  that  we  can  hope  for  com- 
pleteness. There  is  no  necessary  incongruity  between  what 
has  been  accomplished  and  what  remains  to  be  done.  The 
moral  glow  of  Socrates,  which  we  all  feel  by  ignition,  has  in 
it  nothing  incompatible  with  the  physics  of  Anaxagoras 
which  he  so  much  scorned,  but  which  he  would  hardly 
scorn  to-day.  And  here  I  am  reminded  of  one  among  us. 
hoary,  but  still  strong,  whose  prophet-voice  some  thirty  years 
ago,  far  more  than  any  other  of  this  age,  unlocked  whatever 
of  life  and  nobleness  lay  latent  in  its  most  gifted  minds — 
one  fit  to  stand  beside  Socrates  or  the  Maccabean  Eleazar, 
and  to  dare  and  suffer  all  that  they  suffered  and  dared — 
fit,  as  he  once  said  of  Fichte,  '  to  have  been  the  teacher  of 
the  Stoa,  and  to  have  discoursed  of  Beauty  and  Virtue  in 
the  groves  of  Academe.'  "With  a  capacity  to  grasp  physical 
principles  which  his  friend  Goethe  did  not  possess,  and 
which  even  total  lack  of  exercise  has  not  been  able  to  re- 
duce to  atrophy,  it  is  the  world's  loss  that  he,  in  the  vigour 
of  his  years,  did  not  open  his  mind  and  sympathies  to  science, 
and  make  its  conclusions  a  portion  of  his  message  to  man- 
kind. Marvellously  endowed  as  he  was — equally  equipped 
on  the  side  of  the  Heart  and  of  the  Understanding — he 
might  have  done  much  towards  teaching  us  how  to  recon- 
cile the  claims  of  both,  and  to  enable  them  in  coming- 
times  to  dwell  together,  in  unity  of  spirit  and  in  the  bond 
of  peace. 

And  now  the  end  is  come.  With  more  time,  or  greater 
strength  and  knowledge,  what  has  been  here  said  might 
have  been  better  said,  while  worthy  matters,  here  omitted, 
might  have  received  fit  expression.  But  there  would  have 
been  no  material  deviation  from  the  views  set  forth.  As 
regards  myself,  they  are  not  the  growth  of  a  day ;  and  as 


THE  BELFAST   ADDRESS.  633 

regards  you,  I  thought  you  ought  to  know  the  environ- 
ment which,  with  or  without  your  consent,  is  rapidly  sur- 
rounding you,  and  iu  relation  to  which  some  adjustment 
on  your  part  may  be  necessary.  A  hint  of  Hamlet's,  how- 
ever, teaches  us  how  the  troubles  of  common  life  may  be 
ended ;  and  it  is  perfectly  possible  for  you  and  me  to 
purchase  intellectual  peace  at  the  price  of  intellectual 
death.  The  world  is  not  without  refuges  of  this  description  ; 
nor  is  it  wanting  in  persons  who  seek  their  shelter,  and  try 
to  persuade  others  to  do  the  same.  The  unstable  and  the 
weak  have  yielded  and  will  yield  to  this  persuasion,  and 
they  to  whom  repose  is  sweeter  than  the  truth.  But  I 
would  exhort  you  to  refuse  the  offered  shelter,  and  to  scorn 
the  base  repose — to  accept,  if  the  choice  be  forced  upon  you, 
commotion  before  stagnation,  the  breezy  leap  of  the  torrent 
before  the  foetid  stillness  of  the  swamp.  In  the  course  of 
this  Address  I  have  touched  on  debatable  questions,  and  led 
you  over  what  will  be  deemed  dangerous  ground — and  this 
partly  with  the  view  of  telling  you  that,  as  regards  these 
questions,  science  claims  unrestricted  right  of  search.  It 
is  not  to  the  point  to  say  that  the  views  of  Lucretius  and 
Bruno,  of  Darwin  and  Spencer,  may  be  wrong.  Here  I 
should  agree  with  you,  deeming  it  indeed  certain  that 
these  views  will  undergo  modification.  But  the  point  is, 
that,  whether  right  or  wrong,  we  claim  the  right  to  discuss 
them.  For  science,  however,  no  exclusive  claim  is  here 
made  ;  you  are  not  urged  to  erect  it  into  an  idol.  The  in- 
exorable advance  of  man's  understanding  in  the  path  of 
knowledge,  and  those  unquenchable  claims  of  his  moral 
and  emotional  nature,  which  the  understanding  can  never 
satisfy,  are  here  equally  set  forth.  The  world  embraces 
not  only  a  Newton,  but  a  Shakspeare — not  only  a  Boyle, 
but  a  Eaphael — not  only  a  Kant,  but  a  Beethoven — not 
only  a  Darwin,  but  a  Carlyle.  Not  in  each  of  these,  but 
in  all,  is  human  nature  whole.  They  are  not  opposed,  but 


634  FRAGMENTS   OF   SCIENCE. 

supplementary — not  mutually  exclusive,  but  reconcilable. 
And  if,  unsatisfied  with  them  all,  the  human  mind,  with 
the  yearning  of  a  pilgrim  for  his  distant  home,  will  still 
turn  to  the  Mystery  from  which  it  has  emerged,  seeking 
so  to  fashion  it  as  to  give  unity  to  thought  and  faith ;  so 
long  as  this  is  done,  not  only  without  intolerance  or  bigotry 
of  any  kind,  but  with  the  enlightened  recognition  that 
ultimate  fixity  of  conception  is  here  unattainable,  and 
that  each  succeeding  age  must  be  held  free  to  fashion  the 
mystery  in  accordance  with  its  own  needs — then,  casting 
aside  all  the  restrictions  of  Materialism,  I  would  affirm 
this  to  be  a  field  for  the  noblest  exercise  of  what,  in  con- 
trast with  the  knowing  faculties,  may  be  called  the  creative 
faculties  of  man.  Here,  however,  I  touch  a  theme  too 
great  for  me  to  handle,  but  which  will  assuredly  be  handled 
by  the  loftiest  minds,  when  you  and  I,  like  streaks  of 
morning  cloud,  shall  have  melted  into  the  infinite  azure  of 
the  past. 


Prefatory  Remarks. 


AT  the  request  of  my  Publishers,  strengthened  by  the 
expressed  desire  of  many  Correspondents,  I  reprint,  with 
a  few  slight  alterations,  this  Address. 

It  was  written  under  some  disadvantages  this  year  in 
the  Alps,  and  sent  by  instalments  to  the  printer.  "When 
•ead  subsequently  it  proved  too  long  for  its  purpose,  and 
several  of  its  passages  were  accordingly  struck  out.  Some 
of  them  are  here  restored. 

It  has  provoked  an  unexpected  amount  of  criticism. 
This,  in  due  time,  will  subside;  and  I  confidently  look 


PREFACE   TO   THE   BELFAST   ADDEESS.  535 

forward  to  a  calmer  future  for  a  verdict,  founded  not  on 
imaginary  sins,  but  on  the  real  facts  of  the  case. 

Of  the  numberless  strictures  and  accusations,  some  of 
them  exceeding  fierce,  of  which  I  have  been,  and  continue 
to  be,  the  object,  I  refrain  from  speaking  at  any  length. 
To  one  or  two  of  them,  however,  out  of  respect  for  their 
sources,  I  would  ask  permission  briefly  to  refer. 

An  evening  paper  of  the  first  rank,1  after  the  ascription 
to  me  of  various  more  or  less  questionable  aims  and  motives, 
proceeds  to  the  imputation,  that  I  permitted  the  cheers 
of  my  audience  to  '  stimulate '  me  to  the  utterance  of 
words  which  no  right-minded  man,  without  a  sense  of  the 
gravest  responsibility,  could  employ.  I  trust  the  author 
of  this  charge  will  allow  me  in  all  courtesy  to  assure  him 
that  the  words  ascribed  by  him  to  the  spur  of  the  moment 
were  written  in  Switzerland ;  that  they  stood  in  the 
printed  copy  of  the  Address  from  which  I  read,  and  were 
in  the  hands  of  various  London  editors  some  days  previous 
to  the  reading ;  that  they  evoked  no  *  cheers,'  but  a 
silence  far  more  impressive  than  cheers  ;  and  that,  finally, 
as  regards  both  approbation  and  the  reverse,  my  course 
had  been  thought  over,  and  decided,  long  before  I  ventured 
to  address  a  Belfast  audience. 

A  writer  in  an  able  theological  journal  represents 
me  as  '  patting  religion  on  the  back.'  2  The  thought  of 
doing  so  is  certainly  his,  not  mine.  The  facts  of  re- 
ligious feeling  are  to  me  as  certain  as  the  facts  of  physics. 
But  the  world,  I  hold,  will  have  to  distinguish  between 
the  feeling  and  its  forms,  and  to  vary  the  latter  in  accord- 
ance with  the  intellectual  condition  of  the  age. 

I  am  unwilling  to  dwell  upon  statements  ascribed  to 

1  The  '  Pall  Mall  Gazette.' 

*  The  same  journal  was  good  enough  to  speak  with  approval  of  my 
address  on  the  'Scientific  Use  of  the  Imagination,' the  'materialism'  of 
which  is  quite  as  pronounced  as  that  of  the  '  Belfast  Address.' 


536  FRAGMENTS   OF   SCIENCE. 

eminent  men,  which  may  be  imperfectly  reported  in  the 
newspapers,  and  I  therefore  pass  over  a  recent  sermon 
attributed  to  the  Bishop  of  Manchester  with  the  remark, 
that  one  engaged  so  much  as  he  is  in  busy  and,  I  doubt 
not  on  the  whole,  beneficent  outward  life,  is  not  likely  to 
be  among  the  earliest  to  discern  the  more  inward  and 
spiritual  signs  of  the  times,  or  to  prepare  for  the  condition 
which  they  foreshadow. 

In  a  recent  speech  at  Dewsbury,  the  Dean  of  Manches- 
ter is  reported  to  have  expressed  himself  thus  :  *  The  Pro- 
fessor [myself]  ended  a  most  remarkable  and  eloquent 
speech  by  terming  himself  a  material  Atheist.'  My 
attention  was  drawn  to  Dean  Cowie's  statement  by  a 
correspondent,  who  described  it  as  standing  '  conspicuous 
among  the  strange  calumnies '  with  which  my  words  have 
been  assailed.  For  myself  I  use  no  language  which 
could  imply  that  I  am  hurt  by  such  attacks.  They  have 
lost  their  power  to  wound  or  injure.  So  likewise  as  re- 
gards a  resolution  recently  passed  by  the  Presbytery  of 
Belfast,  in  which  Professor  Huxley  and  myself  are  spoken 
of  as  '  ignoring  the  existence  of  God,  and  advocating  pure 
and  simple  materialism ; '  had  the  possessive  pronoun 
'  our '  preceded  '  Grod,'  and  had  the  words  '  what  we  con- 
sider '  preceded  '  pure,'  this  statement  would  have  been 
objectively  true  ;  but  to  make  it  so  this  qualification  is 
required. 

Cardinal  Cullen,  I  am  told,  is  also  actively  engaged  in 
erecting  spiritual  barriers  against  the  intrusion  of  '  Infi- 
delity '  into  Ireland.  His  Eminence,  I  believe,  has  reason 
to  suspect  that  the  Catholic  youth  around  him  are  not 
proof  to  the  seductions  of  science.  Strong  as  he  is,  I 
believe  him  to  be  impotent  here.  The  youth  of  Ireland 
will  imbibe  science,  however  slowly  ;  they  will  be  leavened 
by  it,  however  gradually.  And  to  its  inward  modifying 


PREFACE    TO   THE   BELFAST   ADDRESS.  537 

power  among  Catholics  themselves,  rather  than  to  any 
Protestant  propagandism,  or  other  external  influence,  1 
look  for  the  abatement  of  various  incongruities,  conspicu- 
ous among  which  stand  those  mediaeval  proceedings  which, 
to  the  scandal  and  amazement  of  our  nineteenth  century 
intelligence,  have  been  revived  among  us  during  the  last 
two  years. 

In  connection  with  the  charge  of  Atheism,  I  would 
make  one  remark.  Christian  men  are  proved  by  their 
writings  to  have  their  hours  of  weakness  and  of  doubt,  as 
well  as  their  hours  of  strength  and  of  conviction  ;  and 
men  like  myself  share,  in  their  own  way,  these  variations 
of  mood  and  tense.  Were  the  religious  moods  of  many  of 
my  assailants  the  only  alternative  ones,  I  do  not  know 
how  strong  the  claims  of  the  doctrine  of  'Material  Athe- 
ism '  upon  my  allegiance  might  be.  Probably  they  would 
be  very  strong.  But,  as  it  is,  I  have  noticed  during  years 
of  self-observation  that  it  is  not  in  hours  of  clearness  and 
vigour  that  this  doctrine  commends  itself  to  my  mind ; 
that  in  the  presence  of  stronger  and  healthier  thought  it 
ever  dissolves  and  disappears,  as  offering  no  solution  of 
the  mystery  in  which  we  dwell,  and  of  which  we  form  a 
part. 

To  coarser  attacks  and  denunciations  I  pay  no  atten- 
tion ;  nor  have  I  any  real  reason  to  complain  of  revilings 
addressed  to  me,  which  professing  Christians,  as  could 
readily  be  proved,  do  not  scruple  to  use  towards  each 
other.1 .  The  more  agreeable  task  remains  to  me  of  thank- 

1  I  had  some  notion  of  comparing  at  this  place  the  amenities  of  Chris- 
tian men  towards  each  other,  with  those  of  the  Christian  towards  the  'infidel.' 
I  refrain  from  doing  so,  simply  because  the  samples  before  me,  on  both 
aides  (I  say  it  with  deliberation),  are  too  brutal  to  be  repeated.  Give  me, 
for  my  part,  a  resigned  and  dignified  atheism,  rather  than  a  theism  with 
an  outcome  such  as  this.  It  would,  however,  be  unjust  to  take  these 


638  FRAGMENTS   OP   SCIENCE. 

ing  those  who  have  tried,  however  hopelessly,  to  keep 
accusation  within  the  bounds  of  justice,  and  who,  privately, 
and  at  some  risk  in  public,  have  honoured  me  with  the 
expression  of  their  sympathy  and  approval. 

JOHN  TYHDALL. 

ATHENJKTTM  CLUB  : 

September  15,  1874. 


Prefatory  Remarks. 
II. 

BEING   AN   APOLOGY  POK  THE  BELFAST  ADDRESS. 

I  TAKE  advantage  of  a  pause  in  the  issue  of  this 
Address  to  add  a  few  prefatory  words  to  those  already 
printed. 

The  world  has  been  frequently  informed  of  late  that 
I  have  raised  up  against  myself  a  host  of  enemies ;  and 
considering,  with  few  exceptions,  the  deliverances  of  the 
Press,  and  more  particularly  of  the  religious  Press,  I  am 
forced  to  admit  that  the  statement  is  only  too  true. 
I  derive  some  comfort,  nevertheless,  from  the  reflection 
of  Diogenes,  transmitted  to  us  by  Plutarch,  that '  he  who 
would  be  saved  must  have  good  friends  or  violent  enemies  , 
and  that  he  is  best  off  who  possesses  both.' l  This  '  best ' 
condition,  I  have  reason  to  believe,  is  mine. 

critics  of  the  baser  sort  as  illustrations  of  the  influence  of  theologic  dogma. 
Even  in  this   discussion  liberality  of  thought  and  courtesy  of  language 
have  not  been  wanting  on  the  part  of  some  of  my  opponents.     1875. 
1  '  Fortnightly  Review,'  voL  xiv.  p.  636. 


APOLOGY  FOR  THE  BELFAST  ADDRESS.     639 

Reflecting  on  the  fraction  I  have  read  of  recent  re- 
monstrances, appeals,  menaces,  and  judgments — covering 
not  only  the  world  that  now  is,  but  that  which  is  to 
come — I  have  noticed  with  mournful  interest  how  trivially 
men  seem  to  be  influenced  by  what  they  call  their  religion, 
and  how  potently  by  that  *  nature '  which  it  is  the  alleged 
province  of  religion  to  eradicate  or  subdue.  From  fair 
and  manly  argument,  from  the  tenderest  and  holiest 
sympathy  on  the  part  of  those  who  desire  my  eternal 
good,  I  pass  by  many  gradations,  through  deliberate  un- 
fairness, to  a  spirit  of  bitterness  which  desires  with  a 
fervour  inexpressible  in  words  my  eternal  ill.  Now,  were 
religion  the  potent  factor,  we  might  expect  a  homogeneous 
utterance  from  those  professing  a  common  creed,  while,  if 
human  nature  be  the  really  potent  factor,  we  may  expect 
utterances  as  heterogeneous  as  the  characters  of  men.  As 
a  matter  of  fact  we  have  the  latter ;  suggesting  to  my 
mind  that  the  common  religion,  professed  and  defended 
by  these  different  people,  is  merely  the  accidental  conduit 
through  which  they  pour  their  own  tempers,  lofty  or  low, 
courteous  or  vulgar,  mild  or  ferocious,  as  the  case  may 
be.  Pure  abuse,  however,  as  serving  no  good  end,  I  have, 
wherever  possible,  deliberately  avoided  reading,  wishing, 
indeed,  to  keep,  not  only  hatred,  malice,  uncharitable- 
ness,  but  even  every  trace  of  irritation,  far  away  from 
my  side  of  a  discussion,  which  demands  not  only  good 
temper,  but  largeness,  clearness,  and  many-sidedness  of 
mind,  if  it  is  to  guide  us  even  to  provisional  solutions. 

At  an  early  stage  of  the  controversy,  a  distinguished 
Professor  of  the  University  of  Cambridge  was  understood 
to  argue — and  his  argument  was  caught  up  with  amusing 
eagerness  by  a  portion  of  the  religious  Press — that  my 
ignorance  of  mathematics  renders  me  incompetent  to 
speculate  on  the  proximate  origin  of  life.  Had  I  thought 
his  argument  relevant,  my  reply  would  have  been  simple ; 


540  FRAGMENTS   OF   SCIENCE. 

for  before  me  lies  a  printed  document,  more  than  twenty- 
two  years  old,  bearing  the  signature  of  this  same  learned 
Professor,  in  which  he  was  good  enough  to  testify  that  I 
am  *  well  versed  in  pure  mathematics.' 

It  has  been  stated,  with  many  variations  of  note  and 
comment,  that  in  the  Address  as  published  by  Messrs. 
Longman  I  have  retracted  opinions  uttered  at  Belfast.  A 
Eoman  Catholic  writer  is  specially  strong  upon  this  point. 
Startled  by  the  deep  chorus  of  dissent  which  my  dazzling 
fallacies  have  evoked,  I  am  now  trying  to  retreat.  This 
he  will  by  no  means  tolerate.  '  It  is  too  late  now  to  seek 
to  hide  from  the  eyes  of  mankind  one  foul  blot,  one  ghastly 
deformity.  Professor  Tyndall  has  himself  told  us  how  and 
where  this  Address  of  his  was  composed.  It  was  written 
among  the  glaciers  and  the  solitudes  of  the  Swiss  moun- 
tains. It  was  no  hasty,  hurried,  crude  production  ;  its 
every  sentence  bore  marks  of  thought  and  care.' 

My  critic  intends  to  be  severe  :  he  is  simply  just.  lu 
Che  '  solitudes  '  to  which  he  refers  I  worked  with  delibera- 
tion ;  endeavouring  even  to  purify  my  intellect  by  dis- 
ciplines similar  to  those  enjoined  by  his  own  Church  for 
the  sanctification  of  the  soul.  I  tried,  moreover,  in  my 
ponderings  to  realise  not  only  the  lawful,  but  the  ex- 
pedient ;  and  to  permit  no  fear  to  act  upon  my  mind,  save 
that  of  uttering  a  single  word  on  which  I  could  not  take 
my  stand,  either  in  this  or  in  any  other  world. 

Still  my  time  was  so  brief,  and  my  process  of  thought 
and  expression  so  slow,  that,  in  a  literary  point  of  view, 
I  halted,  not  only  behind  the  ideal,  but  behind  the 
possible.  Hence,  after  the  delivery  of  the  Address,  I  went 
over  it  with  the  desire,  not  to  revoke  its  principles,  but 
to  improve  it  verbally,  and  above  all  to  remove  any  word 
which  might  give  colour  to  the  notion  of  '  heat  and  haste.' 
In  holding  up  as  a  warning  to  writers  of  the  present  the 
errors  and  follies  of  the  denouncers  of  the  past,  I  took 


APOLOGY    FOR   THE   BELFAST   ADDRESS.  641 

occasion  to  compare  the  intellectual  propagation  of  such 
denouncers  to  that  of  thistle-germs  :  the  expression  was 
thought  offensive,  and  I  omitted  it.  It  is  still  omitted 
from  the  Address.  There  was  also  another  passage,  which 
ran  thus :  *  It  is  vain  to  oppose  this  force  [of  religion]  with 
a  view  to  its  extirpation.  What  we  should  oppose,  to  the 
death  if  necessary,  is  every  attempt  to  found  upon  this 
elemental  bias  of  man's  nature,  a  system  which  should 
exercise  despotic  sway  over  his  intellect.  I  do  not  fear 
any  such  consummation.  Science  has  already  to  some 
extent  leavened  the  world,  and  it  will  leaven  it  more  and 
more.  I  should  look  upon  the  mild  light  of  science 
breaking  in  upon  the  minds  of  the  youth  of  Ireland,  and 
strengthening  gradually  to  the  perfect  day,  as  a  surer 
check  to  any  intellectual  or  spiritual  tyranny  which  might 
threaten  this  island,  than  the  laws  of  princes  or  the  swords 
of  emperors.  Where  is  the  cause  of  fear  ?  We  fought 
and  won  our  battle  even  in  the  Middle  Ages ;  why  should 
we  doubt  the  issue  of  a  conflict  now?'' 

This  passage  also  was  deemed  unnecessarily  warm,  and 
I  therefore  omitted  it.  I  fear  it  was  an  act  of  weakness 
on  my  part  to  do  so.  For,  considering  the  aims  and  acts 
of  that  renowned  organisation,  which  for  the  time  being 
wields  the  entire  power  of  my  critic's  Church,  not  only 
resistance  to  its  further  progress,  but,  were  it  not  for  the 
intelligence  of  Koman  Catholic  laymen,  positive  restriction 
of  its  present  power  for  evil,  might  well  become  the 
necessary  attitude  of  society  as  regards  that  organisation. 
With  some  slight  verbal  alterations,  therefore,  which  do 
not  impair  its  strength,  the  passage  has  been  restored. 

My  critic  is  very  hard  upon  the  avowal  in  my  Preface 
regarding  Atheism.  But  I  frankly  confess  that  his  honest 
hardness  and  hostility  are  to  me  preferable  to  the  milder 
but  more  unfair  treatment  which  the  passage  has  received 
from  members  of  other  Churches.  He  quotes  the  para- 


542  FRAGMENTS   OF   SCIENCE. 

graph,  and  goes  on  to  say  :  *  We  repeat  this  is  a  most 
remarkable  passage.  Much  as  we  dislike  seasoning 
polemics  with  strong  words,  we  assert  that  this  Apology 
only  tends  to  affix  with  links  of  steel  to  the  name  of 
Professor  Tyndall,  the  dread  imputation  against  which  he 
struggles.' 

Here  we  have  a  very  fair  example  of  subjective  re- 
ligious vigour.  But  my  quarrel  with  such  exhibitions  is 
that  they  do  not  always  represent  objective  fact.  No 
atheistic  reasoning  can,  I  hold,  dislodge  religion  from 
the  heart  of  man.  Logic  cannot  deprive  us  of  life,  and 
religion  is  life  to  the  religious.  As  an  experience  of  con- 
sciousness it  is  perfectly  beyond  the  assaults  of  logic.  But 
the  religious  life  is  often  projected  in  external  forms — 
I  use  the  word  in  its  widest  sense — and  this  embodiment 
of  the  religious  sentiment  will  have  to  bear  more  and 
more,  as  the  world  becomes  more  enlightened,  the  stress 
of  scientific  tests.  We  must  be  careful  of  projecting  into 
external  nature  that  which  belongs  to  ourselves.  My 
critic  commits  this  mistake :  he  feels,  and  takes  delight 
in  feeling,  that  I  am  struggling,  and  he  obviously  ex- 
periences the  most  exquisite  pleasures  of  '  the  muscular 
sense '  in  holding  me  down.  His  feelings  are  as  real,  as 
if  his  imagination  of  what  mine  are  were  equally  real. 
His  picture  of  my  '  struggles '  is,  however,  a  mere  delusion. 
I  do  not  struggle.  I  do  not  fear  the  charge  of  Atheism  ; 
nor  should  I  even  disavow  it,  in  reference  to  any  definition 
of  the  Supreme  which  he,  or  his  order,  would  be  likely  to 
frame.  His  '  links  '  and  his  '  steel '  and  his  '  dread  im- 
putations'  are,  therefore,  even  more  unsubstantial  than 
my  *  streaks  of  morning  cloud,'  and  they  may  be  permitted 
to  vanish  together. 

Soon  after  the  delivery  of  the  'Belfast  Address '  the  able 
and  respected  Bishop  of  Manchester  did  me  the  honour  of 


APOLOGY   FOR   THE   BELFAST   ADDRESS.  543 

noticing  it ;  and  in  reference  to  that  notice  a  brief  and,  I 
trust,  not  uncourteous  remark  was  introduced  into  my 
first  Preface.  Since  that  time  the  Bishop's  references  to 
me  have  been  very  frequent.  Assuredly  this  is  to  me  an 
unexpected  honour.  Still  a  doubt  may  fairly  be  enter- 
tained whether  this  incessant  speaking  before  public 
assemblies,  on  a  profoundly  emotional  subject,  does  not 
tend  to  disturb  that  equilibrium  of  head  and  heart  which 
it  is  always  so  desirable  to  preserve — whether,  by  giving 
an  injurious  predominance  to  the  feelings,  it  does  not 
tend  to  swathe  the  intellect  in  a  warm  haze,  thus  making 
the  perception,  and  consequent  rendering  of  facts,  in- 
definite, if  not  untrue.  It  was  to  the  Bishop  I  referred 
in  a  recent  brief  discourse  as  'an  able  and,  in  many 
respects,  a  courageous  man  running  to  and  fro  upon  the 
earth,  and  wringing  his  hands  over  the  threatened  loss  • 
of  his  ideals.'  It  is  doubtless  to  this  sorrowing  mood — 
this  partial  and,  I  trust,  temporary  overthrow  of  the 
judgment  by  the  emotions — that  I  must  ascribe  a  pro- 
bably unconscious,  but  still  grave,  misrepresentation,  con- 
tained in  the  Bishop's  last  reference  to  me.  In  the 
'  Times  '  of  November  9  he  is  reported  to  have  expressed 
himself  thus :  *  In  his  lecture  in  Manchester  Professor 
Tyndall  as  much  as  said  that  at  Belfast  he  was  not  in 
his  best  mood,  and  that  his  despondency  passed  away 
in  brighter  moments.'  Now,  considering  that  a  verbatim 
report  of  the  lecture  was  at  hand  in  the  '  Manchester 
Examiner,'  and  that  my  own  corrected  edition  of  it  was 
to  be  had  for  a  penny,  the  Bishop,  I  submit,  might 
nave  afforded  to  repeat  what  I  actually  said,  instead  of 
what  I  '  as  much  as  said.'  I  am  sorry  to  add  that  his 
rendering  of  my  words  is  a  vain  imagination  of  his  own. 
In  my  lecture  at  Manchester  there  was  no  reference,  ex- 
pressed or  implied,  to  my  moods  in  Belfast. 

To  all  earnest  and  honest  minds  acquainted  with  the 


644  FRAGMENTS    OF   SCIENCE. 

paragraph  of  my  first  Preface,1  on  which  the  foregoing 
remark  of  Bishop  Fraser,  and  similar  remarks  of  his 
ecclesiastical  colleagues,  not  to  mention  those  of  less  re- 
sponsible persons,  are  founded,  I  leave  the  decision  of  the 
question,  whether  their  mode  of  presenting  this  paragraph 
to  the  public  be  straightforward  or  the  reverse. 

These  minor  and  more  purely  personal  matters  at  an 
end,  the  weightier  allegation  remains,  that  at  Belfast  I 
misused  my  position  by  quitting  the  domain  of  science, 
and  making  an  unjustifiable  raid  into  the  domain  of 
theology.  This  I  fail  to  see.  Laying  aside  abuse,  I  hope 
my  accusers  will  consent  to  reason  with  me.  Is  it  not 
competent  for  a  scientific  man  to  speculate  on  the  ante- 
cedents of  the  solar  system?  Did  Kant,  Laplace,  and 
•  William  Herschel  quit  their  legitimate  spheres,  when  they 
prolonged  the  intellectual  vision  beyond  the  boundary  of 
experience,  and  propounded  the  nebular  theory  ?  Ac- 
cepting that  theory  as  probable,  is  it  not  permitted  to  a 
scientific  man  to  follow  up,  in  idea,  the  series  of  changes 
associated  with  the  condensation  of  the  nebulae  ;  to  picture 
the  successive  detachment  of  planets  and  moons,  and  the 
relation  of  all  of  them  to  the  sun  ?  If  I  look  upon  our 
earth,  with  its  orbital  revolution  and  axial  rotation,  as 
one  small  issue  of  the  process  which  made  the  solar  system 
what  it  is,  will  any  theologian  deny  my  right  to  entertain 
and  express  this  theoretic  view  ?  Time  was  when  a  multi- 
tude of  theologians  would  be  found  to  do  so — when  that 
arch-enemy  of  science  which  now  vaunts  its  tolerance  would 
have  made  a  speedy  end  of  the  man  who  might  venture 
to  publish  any  opinion  of  the  kind.  But,  that  time,  unless 
the  world  is  caught  strangely  slumbering,  is  for  ever  past. 
As  regards  inorganic  nature,  then,  we  may  traverse, 
without  let  or  hindrance,  the  whole  distance  which  separates 

1  P.  537. 


APOLOGY    FOR   THE   BELFAST    ADDRESS.  545 

the  nebulee  from  the  worlds  of  to-day.  But  only  a  few 
years  ago  this  now  conceded  ground  of  science  was  theo- 
logical ground.  I  could  by  no  means  regard  this  as  the 
final  and  sufficient  concession  of  theology ;  and,  at  Belfast, 
I  thought  it  not  only  my  right  but  my  duty  to  state  that, 
as  regards  the  organic  world,  we  must  enjoy  the  freedom 
which  we  have  already  won  in  regard  to  the  inorganic.  I 
could  not  discern  the  shred  of  a  title-deed  which  gave  any 
man,  or  any  class  of  men,  the  right  to  open  the  door  of 
one  of  these  worlds  to  the  scientific  searcher,  and  to  close 
the  other  against  him.  And  I  considered  it  frankest, 
wisest,  and  in  the  long  run  most  conducive  to  permanent 
peace,  to  indicate,  without  evasion  or  reserve,  the  ground 
that  belongs  to  Science,  and  to  which  she  will  assuredly 
make  good  her  claim. 

Considering  the  freedom  allowed  to  all  manner  of 
opinions  in  England,  surely  this  was  no  extravagant 
position  for  me  to  assume.  I  have  been  reminded  that 
an  eminent  predecessor  of  mine  in  the  Presidential  chair, 
expressed  a  totally  different  view  of  the  Cause  of  things 
from  that  enunciated  by  me.  In  doing  so  he  transgressed 
the  bounds  of  science  at  least  as  much  as  I  did ;  but 
nobody  raised  an  outcry  against  him.  The  freedom  he 
took  I  claim.  And  looking  at  what  I  must  regard  as  the 
extravagances  of  the  religious  world  ;  at  the  very  inade- 
quate and  foolish  notions  concerning  this  universe,  which 
are  entertained  by  the  majority  of  our  authorised  religious 
teachers  ;  at  the  waste  of  energy  on  the  part  of  good  men 
over  things  unworthy,  if  I  might  say  it  without  discourtesy, 
of  the  attention  of  enlightened  heathens  ;  the  fight  about 
the  fripperies  of  Kitualism,  and  the  verbal  quibbles  of  the 
Athanasian  Creed;  the  forcing  on  the  public  view  of 
Pontigny  Pilgrimages  ;  the  dating  of  historic  epochs  from 
the  definition  of  the  Immaculate  Conception  ;  the  pro- 
clamation of  the  Divine  Glories  of  the  Sacred  Heart— 


546  FRAGMENTS    OP   SCIENCE. 

standing  in  the  midst  of  these  chimeras,  which  astound 
all  thinking  men,  it  did  not  appear  to  me  extravagant  to 
claim  the  public  tolerance  for  an  hour  and  a  half,  for  the 
statement  of  more  reasonable  views ;  views  more  in 
accordance  with  the  verities  which  science  has  brought  to 
light,  and  which  many  weary  souls  would,  I  thought, 
welcome  with  gratification  and  relief. 

But  to  come  to  closer  quarters.  The  expression  to 
which  the  most  violent  exception  has  been  taken  is  this  : 
*  Abandoning  all  disguise,  the  confession  I  feel  bound  to 
make  before  you  is,  that  I  prolong  the  vision  backward 
across  the  boundary  of  the  experimental  evidence,  and 
discern  in  that  Matter  which  we,  in  our  ignorance,  and 
notwithstanding  our  professed  reverence  for  its  Creator, 
have  hitherto  covered  with  opprobrium,  the  promise  and 
potency  of  every  form  and  quality  of  life.'  To  call  it  a 
'  chorus  of  dissent,'  as  my  Catholic  critic  does,  is  a  mild 
way  of  describing  the  storm  of  opprobrium  with  which 
this  statement  has  been  assailed.  But  the  first  blast  of 
passion  being  past,  I  hope  I  may  again  ask  my  opponents 
to  consent  to  reason.  First  of  all,  I  am  blamed  for 
crossing  the  boundary  of  the  experimental  evidence. 
This,  I  reply,  is  the  habitual  action  of  the  scientific  mind 
— at  least  of  that  portion  of  it  which  applies  itself  to 
physical  investigation.  Our  theories  of  light,  heat, 
magnetism,  and  electricity,  all  imply  the  crossing  of  this 
boundary.  My  paper  on  the  '  Scientific  Use  of  the  Ima- 
gination,' and  my  'Lectures  on  Light,'  illustrate  this 
point  in  the  amplest  manner  ;  and  in  the  brief  discourse 
which  follows  this  Address  I  have  sought,  incidentally,  to 
make  clear,  that  in  physics  the  experiential  incessantly 
leads  to  the  ultra-experiential;  that  out  of  experience 
there  always  grows  something  finer  than  mere  experience, 
and  that  in  their  different  powers  of  ideal  extension  con- 
sists, for  the  most  part,  the  difference  between  the  great 


APOLOGY   FOE   THE   BELFAST   ADDRESS.  547 

and  the  mediocre  investigator.  The  kingdom  of  science, 
then,  cometh  not  by  observation  and  experiment  alone, 
but  is  completed  by  fixing  the  roots  of  observation  and 
experiment  in  a  region  inaccessible  to  both,  and  in  dealing 
with  which  we  are  forced  to  fall  back  upon  the  picturing 
power  of  the  mind. 

Passing  the  boundary  of  experience,  therefore,  does 
not,  in  the  abstract,  constitute  a  sufficient  ground  for 
censure.  There  must  have  been  something  in  my  par- 
ticular mode  of  crossing  it,  which  provoked  this  tremendous 
'  chorus  of  dissent.' 

Let  us  calmly  reason  the  point  out.  I  hold  the  nebular 
theory  as  it  was  held  by  Kant,  Laplace,  and  William 
Herschel,  and  as  it  is  held  by  the  best  scientific  intellects 
of  to-day.  According  to  it,  our  sun  and  planets  were 
once  diffused  through  space  as  an  impalpable  haze,  out  of 
which,  by  condensation,  came  the  solar  system.  What 
caused  the  haze  to  condense  ?  Loss  of  heat.  What  rounded 
the  sun  and  planets  ?  That  which  rounds  a  tear — mole- 
cular force.  For  seons,  the  immensity  of  which  overwhelms 
man's  conceptions,  the  earth  was  unfit  to  maintain  what 
we  call  life.  It  is  now  covered  with  visible  living  things. 
They  are  not  formed  of  matter  different  from  that  of  the 
earth  around  them.  They  are,  on  the  contrary,  bone  of  its 
bone  and  flesh  of  its  flesh.  How  were  they  introduced  ? 
Was  life  implicated  in  the  nebulae — as  part,  it  may  be,  of 
a  vaster  and  wholly  Unfathomable  Life  ;  or  is  it  the  work 
of  a  Being  standing  outside  the  nebulae,  who  fashioned  it 
and  vitalised  it ;  but  whose  own  origin  and  ways  are  equally 
past  finding  out  ?  As  far  as  the  eye  of  science  has 
hitherto  ranged  through  nature,  no  intrusion  of  purely 
creative  power  into  any  series  of  phenomena  has  ever  beeii 
observed.  The  assumption  of  such  a  power  to  account  for 
special  phenomena,  though  often  made,  has  always  proved 
a  failure.  It  is  opposed  to  the  very  spirit  of  science,  and 


548  FRAGMENTS   OF   SCIENCE. 

I  therefore  assumed  the  responsibility  of  holding  up,  in 
contrast  with  it,  that  method  of  nature  which  it  has  been 
the  vocation  and  triumph  of  science  to  disclose,  and  in 
the  application  of  which  we  can  alone  hope  for  further 
light.  Holding,  then,  that  the  nebulae  and  the  solar 
system,  life  included,  stand  to  each  other  in  the  relation 
of  the  germ  to  the  finished  organism,  I  reaffirm  here,  not 
arrogantly,  or  defiantly,  but  without  a  shade  of  indis- 
tinctness, the  position  laid  down  at  Belfast. 

Not  with  the  vagueness  belonging  to  the  emotions, 
but  with  the  definiteness  belonging  to  the  understanding, 
the  scientific  man  has  to  put  to  himself  these  questions 
regarding  the  introduction  of  life  upon  the  earth.  He 
will  be  the  last  to  dogmatise  upon  the  subject,  for  he 
knows  best  that  certainty  is  here  for  the  present  unattain- 
able. His  refusal  of  the  creative  hypothesis  is  less  an 
assertion  of  knowledge  than  a  protest  against  the  assump- 
tion of  knowledge  which  must  long,  if  not  for  ever,  lie 
beyond  us,  and  the  claim  to  which  is  the  source  of  per- 
petual confusion  upon  earth.  With  a  mind  open  to  con- 
viction he  asks  his  opponents  to  show  him  an  authority 
for  the  belief  they  so  strenuously  and  so  fiercely  uphold. 
They  can  do  no  more  than  point  to  the  Book  of  Genesis, 
or  some  other  portion  of  the  Bible.  Profoundly  interesting, 
and  indeed  pathetic,  to  me  are  those  attempts  of  the 
opening  mind  of  man  to  appease  its  hunger  for  a  Cause. 
But  the  Book  of  Genesis  has  no  voice  in  scientific 
questions.  To  the  grasp  of  geology,  which  it  resisted  for 
a  time,  it  at  length  yielded  like  potter's  clay ;  its  authority 
as  a  system  of  cosmogony  being  discredited  on  all  hands, 
by  the  abandonment  of  the  obvious  meaning  of  its  writer. 
It  is  a  poem,  not  a  scientific  treatise.  In  the  former 
aspect  it  is  for  ever  beautiful :  in  the  latter  aspect  it  has 
been,  and  it  will  continue  to  be,  purely  obstructive  and 
hurtful.  To  knowledge  its  value  has  been  negative, 


APOLOGY    FOR   THE   BELFAST  ADDRESS.  549 

leading,  in  rougher  ages  than  ours,  to  physical,  and  even 
in  our  own  '  free '  age  to  moral,  violence. 

No  incident  connected  with  the  proceedings  at  Belfast 
is  more  instructive  than  the  deportment  of  the  Catholic 
hierarchy  of  Ireland ;  a  body  usually  too  wise  to  confer 
notoriety  upon  an  adversary  by  imprudently  denouncing 
him.  The  '  Times,'  to  which  I  owe  nothing  on  the  score 
of  sympathy,  but  a  great  deal  on  the  score  of  fair  play, 
where  so  much  has  been  unfair,  thinks  that  the  Irish 
Cardinal,  Archbishops,  and  Bishops,  in  the  recent  mani- 
festo, adroitly  employed  a  weapon  which  I,  at  an  unlucky 
moment,  placed  in  their  hands.  The  antecedents  of 
their  action  cause  me  to  regard  it  in  a  different  light ; 
and  a  brief  reference  to  these  antecedents  will,  I  think, 
illuminate  not  only  their  proceedings  regarding  Belfast, 
but  other  doings  which  have  been  recently  noised 
abroad. 

Before  me  lies  a  document,  bearing  the  date  of 
November  187 3,  but  which,  after  appearing  for  a  moment, 
unaccountably  vanished  from  public  view.  It  is  a 
Memorial  addressed  by  Seventy  of  the  Students  and  Ex- 
students  of  the  Catholic  University  in  Ireland,  to  the 
Episcopal  Board  of  the  University;  and  it  constitutes 
the  plainest  and  bravest  remonstrance  ever  addressed  by 
Irish  laymen  to  their  spiritual  pastors  and  masters.  It 
expresses  the  profoundest  dissatisfaction  with  the  cur- 
riculum marked  out  for  the  students  of  the  University ; 
setting  forth  the  extraordinary  fact  that  the  lecture-list 
for  the  faculty  of  Science,  published  a  month  before  they 
wrote,  did  not  contain  the  name  of  a  single  Professor  of 
the  Physical  or  Natural  Sciences. 

The  memorialists  forcibly  deprecate  this,  and  dwell 
upon  the  necessity  of  education  in  science  :  '  The  distin- 
guish ing  mark  of  this  age  is  its  ardour  for  science.  The 


530  FRAGMENTS    OF    SCIENCE. 

natural  sciences  have,  within  the  last  fifty  years,  become 
the  chiefest  study  in  the  world ;  they  are  in  our  time 
pursued  with  an  activity  unparalleled  in  the  history  of 
mankind.  Scarce  a  year  now  passes  without  some  dis- 
covery being  made  in  these  sciences  which,  as  with  the 
touch  of  the  magician's  wand,  shivers  to  atoms  theories 
formerly  deemed  unassailable.  It  is  through  the  physical 
and  natural  sciences  that  the  fiercest  assaults  are  now 
made  on  our  religion.  No  more  deadly  weapon  is  used 
against  our  faith  than  the  facts  incontestably  proved  by 
modern  researches  in  science.' 

Such  statements  must  be  the  reverse  of  comfortable 
to  a  number  of  gentlemen  who,  trained  in  the  philosophy 
of  Thomas  Aquinas,  have  been  accustomed  to  the  un- 
questioning submission  of  all  other  sciences  to  their 
divine  science  of  Theology.  But  something  more  remains : 
4  One  thing  seems  certain,'  say  the  memorialsts,  viz.,  '  that 
if  chairs  for  the  physical  and  natural  sciences  be  not  soon 
founded  in  the  Catholic  University,  very  many  young 
men  will  have  their  faith  exposed  to  dangers  which  the 
creation  of  a  school  of  science  in  the  University  would 
defend  them  from.  For  our  generation  of  Irish  Catholics 
are  writhing  under  the  sense  of  their  inferiority  in 
science,  and  are  determined  that  such  inferiority  shall 
not  long  continue  ;  and  so,  if  scientific  training  be  un- 
attainable at  our  University,  they  will  seek  it  at  Trinity, 
or  at  the  Queen's  Colleges,  in  not  one  of  which  is  there 
a  Catholic  Professor  of  Science.' 

Those  who  imagined  the  Catholic  University  at  Ken- 
sington to  be  due  to  the  spontaneous  recognition,  on  the 
part  of  the  Eoman  hierarchy,  of  the  intellectual  needs  of 
the  age,  will  derive  enlightenment  from  this,  and  still  more 
from  what  follows :  for  the  most  formidable  threat  remains. 
To  the  picture  of  Catholic  students  seceding  to  Trinity  and 
the  Queen's  Colleges,  the  memorialists  add  this  darkest 


APOLOGY  FOR  THE  BELFAST  ADDRESS.     551 

stroke  of  all :  « They  will,  in  the  solitude  of  their  own 
homes,  unaided  by  any  guiding  advice,  devour  the  works 
of  Hseckel,  Darwin,  Husley,  Tyndall,  and  Lyell ;  works 
innocuous  if  studied  under  a  professor  who  would  point 
out  the  difference  between  established  facts  and  erroneous 
inferences,  but  which  are  calculated  to  sap  the  faith  of 
a  solitary  student,  deprived  of  a  discriminating  judg- 
ment to  which  he  could  refer  for  a  solution  of  his  diffi- 
culties.' 

In  the  light  of  the  knowledge  given  by  this  courageous 
memorial,  and  of  similar  knowledge  otherwise  derived, 
the  recent  Catholic  manifesto  did  not  at  all  strike  me  as 
a  chuckle  over  the  mistake  of  a  maladroit  adversary,  but 
rather  as  an  evidence  of  profound  uneasiness  on  the  part 
of  the  Cardinal,  the  Archbishops,  and  the  Bishops  who 
signed  it.  They  acted  towards  it,  however,  with  their 
accustomed  practical  wisdom.  As  one  concession  to  the 
spirit  which  it  embodied,  the  Catholic  University  at  Ken- 
sington was  brought  forth,  apparently  as  the  effect  of 
spontaneous  inward  force,  and  not  of  outward  pressure, 
which  was  rapidly  becoming  too  formidable  to  be  success- 
fully opposed. 

The  memorialists  point  with  bitterness  to  the  fact, 
that '  the  name  of  no  Irish  Catholic  is  known  in  connection 
with  the  physical  and  natural  sciences.'  But  this,  they 
ought  to  know,  is  the  complaint  of  free  and  cultivated 
minds  wherever  a  Priesthood  exercises  dominant  power. 
Precisely  the  same  complaint  has  been  made  with  re- 
spect to  the  Catholics  of  Germany.  The  great  national 
literature  and  scientific  achievements  of  that  country,  in 
modern  times,  are  almost  wholly  the  work  of  Protestants. 
A  vanishingly  small  fraction  of  it  only  is  derived  from 
members  of  the  Eoman  Church,  although  the  number  of 
these  in  Germany  is  at  least  as  great  as  that  of  the  Pro- 
testants. *  The  question  arises,'  says  a  writer  in  an  able 


652  FRAGMENTS    OF   SCIENCE. 

German  periodical,  '  what  is  the  cause  of  a  phenomenon 
so  humiliating  to  the  Catholics  ?  It  cannot  be  referred 
to  want  of  natural  endowment  due  to  climate  (for  the 
Protestants  of  Southern  Germany  have  contributed  power- 
fully to  the  creations  of  the  German  intellect),  but  purely 
to  outward  circumstances.  And  these  are  readily  dis- 
covered in  the  pressure  exercised  for  centuries  by  the 
Jesuitical  system,  which  has  crushed  out  of  Catholics 
every  tendency  to  free  mental  productiveness.'  It  is, 
indeed,  in  Catholic  countries  that  the  weight  of  Ultra- 
montanism  has  been  most  severely  felt.  It  is  in  such 
countries  that  the  very  finest  spirits,  who  have  dared, 
without  quitting  their  faith,  to  plead  for  freedom  or 
reform,  have  suffered  extinction.  The  extinction,  how- 
ever, was  more  apparent  than  real,  and  Hermes,  Hirscher, 
and  Giinther,  though  individually  broken  and  subdued, 
prepared  the  way,  in  Bavaria,  for  the  persecuted  but  un- 
flinching Frohschammer,  for  Dollinger,  and  for  the  re- 
markable liberal  movement  of  which  Dollinger  is  the 
head  and  guide. 

Though  moulded  for  centuries  to  an  obedience  un- 
paralleled in  any  other  country,  except  Spain,  the  Irish 
intellect  is  beginning  to  show  signs  of  independence; 
demanding  a  diet  more  suited  to  its  years  than  the 
pabulum  of  the  Middle  Ages.  As  for  the  recent  mani- 
festo in  which  Pope,  Cardinal,  Archbishops,  and  Bishops 
are  united  in  one  grand  anathema,  its  character  and 
fate  are  shadowed  forth  by  the  Vision  of  Nebuchadnezzar 
recorded  in  the  Book  of  Daniel.  It  resembles  the  image 
whose  form  was  terrible,  but  the  gold,  and  silver,  and 
brass,  and  iron  of  which  rested  upon  feet  of  clay.  And  a 
stone  smote  the  feet  of  clay ;  and  the  iron,  and  the  brass, 
and  the  silver,  and  the  gold,  were  broken  in  pieces  to- 
gether, and  became  like  the  chaff  of  the  summer  thresh- 
ing-floors, and  the  wind  carried  them  away. 


Al'OLOGY   FOR   THE   BELFAST   ADDRESS.  553 

Monsignor  Capel  has  recently  been  good  enough  to  pro- 
claim at  once  the  friendliness  of  his  Church  towards  true 
science,  and  her  right  to  determine  what  true  science  is. 
Let  us  dwell  for  a  moment  on  the  proofs  of  her  scientific 
competence.  When  Halley'y  comet  appeared  in  1456  it 
was  regarded  as  the  harbinger  of  God's  vengeance,  the 
dispenser  of  war,  pestilence,  and  famine,  and  by  order  of 
the  Pope  the  church  bells  of  Europe  were  rung  to  scare 
the  monster  away.  An  additional  daily  prayer  was  added 
to  the  supplications  of  the  faithful.  The  comet  in  due 
time  disappeared,  and  the  faithful  were  comforted  by  the 
assurance  that,  as  in  previous  instances  relating  to  eclipses, 
droughts,  and  rains,  so  also  as  regards  this  'nefarious' 
comet,  victory  had  been  vouchsafed  to  the  Church. 

Both  Pythagoras  and  Copernicus  had  taught  the 
heliocentric  doctrine — that  the  earth  revolves  round  the 
sun.  In  the  exercise  of  her  right  to  determine  what  true 
science  is,  the  Church,  in  the  Pontificate  of  Paul  V., 
stepped  in,  and  by  the  mouth  of  the  holy  Congregation  of 
the  Index,  delivered,  on  March  5,  1616,  the  following 
decree : — 

And  ivhereas  it  hath  also  come  to  the  knowledge  of  the 
said  holy  congregation  that  the  false  Pythagorean  doctrine 
of  the  mobility  of  the  earth  and  the  immobility  of  the  sun, 
entirely  opposed  to  Holy  writ,  which  is  taught  by  Nicolas 
Copernicus,  is  now  published  abroad  and  received  by 
many.  In  order  that  this  opinion  may  not  further 
spread,  to  the  damage  of  Catholic  truth,  it  is  ordered  that 
this  and  all  other  books  teaching  the  like  doctrine  be  sus- 
pended, and  by  this  decree  they  are  all  respectively  sus- 
pended, forbidden,  and  condemned. 

But  why  go  back  to  1456  and  1616  ?  Far  be  it  from 
me  to  charge  bygone  sins  upon  Monsignor  Capel,  were  it 
not  for  the  practices  he  upholds  to-day.  The  most 
applauded  dogmatist  and  champion  of  the  Jesuits  is,  I  am 


654  FRAGMENTS   OP   SCIENCE. 

informed,  Perrone.  No  less  than  thirty  editions  of  a  work 
of  his  have  been  scattered  abroad  for  the  healing  of 
the  nations.  His  notions  of  physical  astronomy  are 
virtually  those  of  1456.  He  teaches  boldly  that  'God 
does  not  rule  by  universal  law  .  .  .  that  when  God 
orders  a  given  planet  to  stand  still  He  does  not  detract 
from  any  law  passed  by  Himself,  but  orders  that  planet 
to  move  round  the  sun  for  such  and  such  a  time,  then  to 
stand  still,  and  then  again  to  move,  as  His  pleasure  may 
be.'  Jesuitism  proscribed  Frohschammer  for  questioning 
its  favourite  dogma,  that  every  human  soul  was  created 
by  a  direct  supernatural  act  of  God,  and  for  asserting 
that  man,  body  and  soul,  came  from  his  parents.  This 
is  the  system  that  now  strives  for  universal  power ;  it 
is  from  it,  as  Monsignor  Capel  graciously  informs  us,  that 
we  are  to  learn  what  is  allowable  in  science,  and  what 
is  not ! 

In  the  face  of  such  facts,  which  might  be  multiplied 
at  will,  it  requires  extraordinary  bravery  of  mind,  or  a 
reliance  upon  public  ignorance  almost  as  extraordinary, 
to  make  the  claims  made  by  Monsignor  Capel  for  his 
Church. 

A  German  author,  speaking  of  one  who  has  had  bitter 
experience  in  this  line,  describes  those  Catholic  writers  who 
refuse  to  submit  to  the  Congregation  of  the  Index  as  out- 
lawed— fair  subjects  for  moral  assassination.1  This  is  very 
strong ;  and  still,  judging  from  my  own  small  experience, 
not  too  strong.  In  reference  to  this  I  would  ask,  not  with- 
out special  reason,  indulgence  for  a  brief  personal  allusion 
here.  It  will  serve  a  twofold  object,  one  of  which  will  be 

1  See  the  case  of  Frohgchammer  as  sketched  by  a  friend  in  the  Preface 
to  '  Christenthum  und  die  moderne  Wissenschaft.'  His  enemies  contrived 
to  take  his  bread,  in  great  part,  away,  but  they  failed  to  subdue  him,  and 
not  even  the  Pope's  Nuncio  could  prevent  five  hundred  students  of  the 
University  of  Munich  from  signing  an  Address  to  their  Professor. 


APOLOGY    FOR   THE   BELFAST   ADDRESS.  565 

manifest,  the  other  being  reserved  for  future  treatment. 
Sprung  from  a  source  to  which  the  Bible  was  specially 
dear,  my  early  training  was  confined  almost  exclusively  to 
it.  Born  in  Ireland,  I,  like  my  predecessors  for  many 
generations,  was  taught  to  hold  my  own  against  the  Church 
of  Eome.  I  had  a  father  whose  memory  ought  to  be  to 
me  a  stay,  and  an  example  of  unbending  rectitude  and 
purity  of  life.  The  small  stock  to  which  he  belonged 
were  scattered  with  various  fortunes  along  that  eastern 
rim  of  Leinster,  from  Wexford  upwards,  to  which  they 
crossed  from  the  Bristol  Channel.  My  father  was  the 
poorest  of  them.  Socially  low,  but  mentally  and  morally 
high  and  independent,  by  his  own  inner  energies  and  affi- 
nities he  obtained  a  knowledge  of  history  which  would  put 
mine  to  shame ;  while  the  whole  of  the  controversy  between 
Protestantism  and  Romanism  was  at  his  fingers'  ends.  At 
the  present  moment  the  works  and  characters  which 
occupied  him  come,  as  far-off  recollections,  to  my  mind. 
Claude  and  Bossuet,  Chillingworth  and  Nott,  Tillotson, 
Jeremy  Taylor,  Challoner  and  Milner,  Pope  and  McGuire, 
and  others  whom  I  have  forgotten,  or  whom  it  is  needless 
to  name.  Still  this  man,  so  charged  with  the  ammunition 
of  controversy,  was  so  respected  by  his  Catholic  fellow- 
townsmen,  that  they  one  and  all  put  up  their  shutters 
when  he  died. 

With  such  a  preceptor,  and  with  an  hereditary  interest 
in  the  Papal  controversy,  I  naturally  went  into  it.  I  did 
not  confine  myself  to  the  Protestant  statement  of  the 
question,  but  made  myself  also  acquainted  with  the  argu- 
ments of  the  Church  of  Rome.  I  remember  to  this  hour 
the  interest  and  surprise  with  which  I  read  Challoner's 
*  Catholic  Christian  Instructed ; '  and  on  the  border-line 
between  boyhood  and  manhood  I  was  to  be  found  taking 
part  in  controversies,  in  which  the  rival  faiths  were  pitted 
against  each  other.  I  sometimes  took  the  Catholic  side, 
26 


566  FEAGMENTS    OF   SCIENCE. 

and  gave  my  Protestant  antagonist  considerable  trouble. 
The  views  of  Irish  Catholics  became  thus  intimately  known 
to  me,  and  there  was  no  doctrine  of  Protestantism  which 
they  more  emphatically  rejected,  and  the  ascription  of 
which  to  them  they  resented  more  warmly,  than  the 
doctrine  of  the  Pope's  personal  infallibility.  Yet  in  the 
face  of  this  knowledge  it  was  obstinately  asserted  and  re- 
asserted in  my  presence  some  time  ago,  by  a  Catholic 
priest,  that  the  doctrine  of  the  infallibility  of  the  Pope 
had  always  been  maintained  in  Ireland.1 

But  this  is  an  episode,  intended  to  disabuse  those  who, 
in  this  country  or  the  United  States,  may  have  been  mis- 
led by  reckless  persons,  in  regard  to  the  personal  points 
referred  to.  I  now  return  to  the  impersonal.  The  course 
of  life  upon  earth,  as  far  as  Science  can  see,  has  been  one 
of  amelioration — a  steady  advance  on  the  whole  from  the 
lower  to  the  higher.  The  continued  effort  of  animated 
nature  is  to  improve  its  condition  and  raise  itself  to  a 
loftier  level.  In  man  improvement  and  amelioration 
depend  largely  upon  the  growth  of  conscious  knowledge, 
by  which  the  errors  of  ignorance  are  continually  moulted, 
and  truth  is  organised.  It  is  assuredly  the  advance  of 
knowledge  that  has  given  a  materialistic  colour  to  the 
philosophy  of  this  age.  Materialism  is  therefore  not  a 
thing  to  be  mourned  over,  but  to  be  honestly  considered — 
accepted  if  it  be  wholly  true,  rejected  if  it  be  wholly  false, 
wisely  sifted  and  turned  to  account  if  it  embrace  a 
mixture  of  truth  and  error.  Of  late  years  the  study  of  the 
nervous  system,  and  its  relation  to  thought  and  feeling, 
Lave  profoundly  occupied  enquiring  minds.  It  is  our 

1  On  a  memory  which  dates  back  to  my  fifteenth  year,  -when  I  first 
read  the  discussion  between  Mr.  Pope  and  Father  McGuire,  I  should  be 
inclined  to  rely  for  proof  that  the  Catholic  clergyman,  in  that  discussion, 
and  in  the  name  of  his  Church,  repudiated  the  doctrine  of  personal  in- 
fallibility. 


APOLOGY  FOR  THE   BELFAST   ADDRESS.  557 

duty  not  to  shirk — it  ought  rather  to  be  our  privilege  to 
accept — the  established  results  of  such  enquiries,  for  here 
assuredly  our  ultimate  weal  depends  upon  our  loyalty  to 
the  truth.  Instructed  as  to  the  control  which  the  nervous 
system  exercises  over  man's  moral  and  intellectual  nature, 
we  shall  be  better  prepared,  not  only  to  mend  their  mani- 
fold defects,  but  also  to  strengthen  and  purify  both.  Is 
mind  degraded  by  this  recognition  of  its  dependence  ? 
Assuredly  not.  Matter,  on  the  contrary,  is  raised  to  the 
level  it  ought  to  occupy,  and  from  which  timid  ignorance 
would  remove  it. 

But  the  light  is  dawning,  and  it  will  become  stronger 
as  time  goes  on.  Even  the  Brighton  Congress  affords 
evidence  of  this.  From  the  manifold  confusions  of  that 
assemblage  my  memory  has  rescued  two  items,  which  it 
would  fain  preserve :  the  recognition  of  a  relation  between 
Health  and  Eeligion,  and  the  address  of  the  Rev.  Harry 
Jones.  Out  of  the  conflict  of  vanities  his  words  emerge 
wholesome  and  strong,  because  undrugged  by  dogma, 
coming  directly  from  the  warm  brain  of  one  who  knows 
what  practical  truth  means,  and  who  has  faith  in  its 
vitality  and  inherent  power  of  propagation.  I  wonder  is 
he  less  effectual  in  his  ministry  than  his  more  embroidered 
colleagues  ?  It  surely  behoves  our  teachers  to  come  to  some 
definite  understanding  as  to  this  question  of  health ;  to 
see  how,  by  inattention  to  it,  we  are  defrauded,  negatively 
and  positively :  negatively,  by  the  privation  of  that 
'  sweetness  and  light '  which  is  the  natural  concomitant 
of  good  health  ;  positively,  by  the  insertion  into  life  of 
cynicism,  ill-temper,  and  a  thousand  corroding  anxieties 
which  good  health  would  dissipate.  We  fear  and  scorn 
*  materialism.'  But  he  who  knew  all  about  it,  and  could 
apply  his  knowledge,  might  become  the  preacher  of  a  ne\\ 
gospel.  Not,  however,  through  the  ecstatic  moments  of 
t'tie  individual  does  such  knowledge  come,  but  through 


668  FRAGMENTS   OF   SCIENCE. 

the  revelations  of  science,  in  connection  with  the  history 
of  mankind. 

Why  should  the  Eoman  Catholic  Church  call  gluttony 
a  mortal  sin  ?  Why  should  fasting  occupy  a  place  in  the 
disciplines  of  religion  ?  What  is  the  meaning  of  Luther's 
advice  to  the  young  clergyman  who  came  to  him,  perplexed 
with  the  difficulties  of  predestination  and  election,  if  it 
be  not  that,  in  virtue  of  its  action  upon  the  brain,  when 
wisely  applied,  there  is  moral  and  religious  virtue  even 
in  a  hydro-carbon  ?  To  use  the  old  language,  food  and 
drink  are  creatures  of  God,  and  have  therefore  a  spiritual 
value.  The  air  of  the  Alps  would  be  augmented  tenfold 
in  purifying  power  if  this  truth  were  recognised.  Through 
our  neglect  of  the  monitions  of  a  reasonable  materialism 
we  sin  and  suffer  daily.  I  might  here  point  to  the  train 
of  deadly  disorders  over  which  science  has  given  modern 
society  such  control — disclosing  the  lair  of  the  material 
enemy,  ensuring  his  destruction,  and  thus  preventing  that 
moral  squalor  and  hopelessness  which  habitually  tread  on 
the  heels  of  epidemics  in  the  case  of  the  poor. 

Eising  to  higher  spheres,  the  visions  of  Swedenborg, 
and  the  ecstacy  of  Plotinus  and  Porphyry,  are  phases  of 
that  psychical  condition,  obviously  connected  with  the 
nervous  system  and  state  of  health,  on  which  is  based  the 
Vedic  doctrine  of  the  absorption  of  the  individual  into 
the  universal  soul.  Plotinus  taught  the  devout  how  to 
pass  into  a  condition  of  ecstasy.  Porphyry  complains  of 
having  been  only  once  united  to  God  in  eighty-six  years, 
while  his  master  Plotinus  had  been  so  united  six  times  in 
sixty  years.1  A  friend  who  knew  Wordsworth  informs 

1  I  recommend  to  the  reader's  particular  attention  Dr.  Draper's  impor- 
tant work  entitled,  '  History  of  the  Conflict  between  Religion  and  Science ' 
(Messrs.  H.  S.  King  and  Co.).  There,  in  small  compass,  will  be  found  a 
description  of  the  long  continued  struggle  between  Science  and  the  Romish 
Church. 


APOLOGY   FOR   THE   BELFAST   ADDRESS.  559 

me  that  the  poet,  in  some  of  his  moods,  was  accustomed 
to  seize  hold  of  an  external  object  to  assure  himself  of  his 
own  bodily  existence.  No  one,  I  should  say,  has  had  a 
wider  experience  in  this  field  than  Mr.  Emerson.  As 
states  of  consciousness  those  phenomena  have  an  undis- 
puted reality,  and  a  substantial  identity ;  but  they  are 
connected  with  the  most  heterogeneous  objective  concep- 
tions. The  subjective  experiences  are  similar,  because  ot 
the  similarity  of  the  underlying  nervous  organisations. 

But  for  those  who  wish  to  look  beyond  the  practical 
facts,  there  will  always  remain  ample  room  for  speculation. 
Take  the  argument  of  the  Lucretian  introduced  in  the 
foregoing  Address  at  page  498.  As  far  as  I  am  aware,  not 
one  of  my  assailants  has  attempted  to  answer  it.  Some 
of  them,  indeed,  rejoice  over  the  ability  displayed  by 
Bishop  Butler  in  rolling  back  the  difficulty  on  his  opponent ; 
and  they  even  imagine  that  it  is  the  Bishop's  own  argu- 
ment that  is  there  employed.  Instructed  by  self-know- 
ledge, they  can  hardly  credit  me  with  the  wish  to  state 
both  sides  of  the  question  at  issue ;  and  to  show  by 
reasoning,  stronger  than  Butler  ever  used,  the  overthrow 
which  awaits  any  doctrine  of  materialism  based  upon 
the  definitions  of  matter  habitually  received.  But  the 
raising  of  a  new  difficulty  does  not  abolish—  does  not 
even  lessen — the  old  one,  and  the  argument  of  the 
Lucretian  remains  untouched  by  anything  the  Bishop  has 
said  or  can  say. 

And  here  it  may  be  permitted  me  to  add  a  word  to  an 
important  controversy  now  going  on.  In  an  article  on 
*  Physics  and  Metaphysics,'  published  in  the  *  Saturday 
Review'  more  than  fourteen  years  ago  [1860],  I  ventured  to 
state  thus  the  old  problem  of  the  relation  of  physics  to  con- 
sciousness :  '  The  philosophy  of  the  future  will  assuredly 
take  more  account  than  that  of  the  past,  of  the  relation  of 
thought  and  feeling  to  physical  processes ;  and,  it  may  be, 


500  FRAGMENTS   OF   SCIENCE. 

that  the  qualities  of  Mind  will  be  studied  through  the 
organism,  as  we  now  study  the  character  of  Force  through 
the  affections  of  ordinary  matter.  We  believe  that  every 
thought  and  every  feeling  has  its  definite  mechanical 
correlative  in  the  nervous  system — that  it  is  accompanied 
by  a  certain  Reparation  and  remarshalling  of  the  atoms  of 
the  brain. 

1  This  latter  process  is  purely  physical ;  and  were  the 
faculties  we  now  possess  sufficiently  strengthened,  without 
the  creation  of  any  new  faculty,  it  would  doubtless  be 
within  the  range  of  our  augmented  powers  to  infer  from 
the  molecular  state  of  the  brain,  the  character  of  the 
thought  acting  upon  it;  and,  conversely,  to  infer  from 
the  thought,  the  exact  corresponding  molecular  condition 
of  the  brain.  We  do  not  say — and  this,  as  will  be  seen, 
is  all-important — that  the  inference  here  referred  to 
would  be  an  a  priori  one.  What  we  say  is,  that  by 
observing,  with  the  faculties  we  assume,  the  state  of  the 
brain,  and  the  associated  mental  affections,  both  might 
be  so  tabulated  side  by  side,  that  if  one  were  given,  a 
mere  reference  to  the  table  would  declare  the  other. 

'  Given  the  masses  of  the  planets  and  their  distances 
asunder,  and  we  can  infer  the  perturbations  consequent  on 
their  mutual  attractions.  Given  the  nature  of  a  disturb- 
ance in  water,  air,  or  aether,  and  from  the  physical  pro- 
perties of  the  medium  we  can  infer  how  its  particles  will 
be  affected.  The  mind  runs  along  the  line  of  thought 
which  connects  the  phenomena,  and  from  beginning  to 
end  finds  no  break  in  the  chain.  But  when  we  endeavour 
to  pass,  by  a  similar  process,  from  the  physics  of  the  brain 
to  the  phenomena  of  consciousness,  we  meet  a  problem 
which  transcends  every  conceivable  expansion  of  the  powers 
we  now  possess.  We  may  think  over  the  subject  again 
and  again;  it  eludes  all  intellectual  presentation — we 
stand  at  length  face  to  face  with  the  Incomprehensible.' 


APOLOGY   FOR   THE   BELFAST   ADDRESS.  561 

The  discussion  above  referred  to  turns  on  the  question : 
Do  states  of  consciousness  enter  as  links  into  the  chain  of 
antecedence  and  sequence,  which  give  rise  to  bodily  actions, 
and  to  other  states  of  consciousness ;  or  are  they  merely 
by-products,  which  are  not  essential  to  the  physical 
processes  going  on  in  the  brain  ?  Speaking  for  myself,  it 
is  certain  that  I  have  no  power  of  imagining  states  of 
consciousness,  interposed  between  the  molecules  of  the 
brain,  and  influencing  the  transference  of  motion  among 
the  molecules.  The  thought c  eludes  all  mental  presenta- 
tion ; '  and  hence  the  logic  seems  of  iron  strength  which 
claims  for  the  brain  an  automatic  action,  uninfluenced  by 
states  of  consciousness.  But  it  is,  I  believe,  admitted  by 
those  who  hold  the  automaton-theory,  that  states  of 
consciousness  are  produced  by  the  marshalling  of  the 
molecules  of  the  brain;  and  this  production  of  conscious- 
ness by  molecular  motion  is  to  me  quite  as  unthinkable 
as  the  production  of  molecular  motion  by  consciousness. 
If,  therefore,  unthinkability  be  the  proper  test,  I  must 
equally  reject  both  classes  of  phenomena.  I,  however, 
reject  neither,  and  thus  stand  in  the  presence  of  two  In- 
comprehensibles,  instead  of  one  Incomprehensible.  While 
accepting  fearlessly  the  facts  of  materialism  dwelt  upon  in 
these  pages,  I  bow  my  head  in  the  dust  before  that 
mystery  of  mind,  which  has  hitherto  defied  its  own  pene- 
trative power,  and  which  may  ultimately  resolve  itself  into 
a  demonstrable  impossibility  of  self-penetration. 

But  the  secret  is  an  open  one — the  practical  monitions 
are  plain  enough,  which  declare  that  on  our  dealings  with 
matter  depends  our  weal  or  woe,  physical  and  moral. 
The  state  of  mind  which  rebels  against  the  recognition  of 
the  claims  of  '  materialism '  is  not  unknown  to  me.  I 
can  remember  a  time  when  I  regarded  my  body  as  a  weed, 
so  much  more  highly  did  I  prize  the  conscious  strength 
and  pleasure  derived  from  moral  and  religious  feeling 


602  FRAGMENTS   OP   SCIENCE. 

— which,  I  may  add,  was  mine  without  the  intervention  of 
dogma.  The  error  was  not  an  ignoble  one,  but  this  did 
not  save  it  from  the  penalty  attached  to  error.  Saner 
knowledge  taught  me  that  the  body  is  no  weed,  and  that 
if  it  were  treated  as  such  it  would  infallibly  avenge  itself. 
Am  I  personally  lowered  by  this  change  of  front  ?  Not 
so.  Give  me  their  health,  and  there  is  no  spiritual  ex- 
perience of  those  earlier  years — no  resolve  of  duty,  or 
work  of  mercy,  no  act  of  self-renouncement,  no  solemnity 
of  thought,  no  joy  in  the  life  and  aspects  of  nature — that 
would  not  still  be  mine;  and  this  without  the  least 
reference  or  regard  to  any  purely  personal  reward  or  pun- 
ishment looming  in  the  future. 

As  I  close  these  remarks,  the  latest  utterances  of  the 
Bishop  of  Peterborough  reach  me.  I  observe  with  regret 
that,  notwithstanding  all  their  '  expansiveness,'  both  he 
and  his  Eight  Eev.  Brother  of  Manchester,  appear  to 
know  almost  as  little  of  the  things  which  belong  to  our 
peace,  as  that  frenzied  ritualist  who,  a  day  or  two  ago, 
raised  the  cry  of  '  excommunicated  heretic  ! '  against  the 
Bishop  of  Natal.  Happily  we  have  amongst  us  our 
Jowetts  and  our  Stanleys,  not  to  mention  other  brave 
men,  who  see  more  clearly  the  character  and  magnitude 
of  the  coming  struggle  ;  and  who  believe  undoubtingly 
that  out  of  it  the  truths  of  science  will  emerge  with  heal- 
ing in  their  wings. 

And  now  I  have  to  utter  a  *  farewell '  free  from 
bitterness  to  all  my  readers ;  thanking  my  friends  for  a 
sympathy  more  steadfast,  I  would  fain  believe,  if  less  noisy, 
than  the  antipathy  of  my  foes  ;  and  commending  to  these 
a  passage  from  Bishop  Butler,  which  they  have  either 
not  read  or  failed  to  lay  to  heart.  '  It  seems,'  saith 
the  Bishop,  « that  men  would  be  strangely  headstrong  and 
self-willed,  and  disposed  to  exert  themselves  with  an 
impetuosity  which  would  render  society  insupportable, 


APOLOGY   FOR   THE   BELFAST   ADDRESS.  563 

and  the  living  in  it  impracticable,  were  it  not  for  some 
acquired  moderation  and  self-government,  some  aptitude 
and  readiness  in  restraining  themselves,  and  concealing 
their  sense  of  things.'  In  temperance  of  language,  at 
least,  his  Grace  the  Archbishop  of  Canterbury  has  set  a 
good  example.1 

JOHN  TYNDALL. 

ATHEK^EUM  CLUB: 

December  5,  1874. 

A  still  more  remarkable  illustration  of  absence  of  vituperation,  asso- 
ciated -with  real  scientific  insight,  is  furnished  by  the  sermon  of  the  Bishop 
of  Carlisle,  reported  in  the  '  Oxford  University  Herald '  for  November  28, 
1874.  To  Dr.  Quarry,  and  to  a  contributor  in  the  current  number  of 
the  'British  Quarterly  Review,'  my  special  acknowledgments  are  due. 
(November,  1875.) 


564  FRAGMENTS   OF   SCIENCE. 


VIII. 
CRYSTALS  AND  MOLECULAR  FORCE. 

1874. 

A  FEW  years  ago  I  paid  a  visit  to  a  large  school  in  the 
country,  and  was  asked  by  the  principal  to  give  a 
lesson  to  one  of  the  classes.  I  agreed  to  do  so,  provided 
he  would  let  me  have  the  youngest  hoys  in  his  school. 
To  this  he  willingly  assented  :  and,  after  casting  about  in 
my  mind  as  to  what  could  be  said  to  the  little  fellows, 
I  went  to  a  village  hard  by  and  brought  some  sugar- 
candy.  This  was  my  teaching  apparatus.  The  boys  hav- 
ing assembled,  I  began  by  describing  the  way  in  which 
sugar-candy  and  other  artificial  crystals  are  formed,  and 
tried  to  place  vividly  before  their  young  minds  the  archi- 
tectural process  by  which  crystals  are  built  up.  They 
listened  to  me  with  eager  interest.  I  examined  the 
crystal  before  them,  pointing  out  its  various  faces  and 
angles ;  and  when  they  found  that  in  a  certain  direction  it 
could  be  split  into  thin  laminae  with  shining  surfaces  of 
cleavage,  their  joy  was  at  its  height.  They  had  no 
notion  that  the  thing  they  had  been  crunching  and 
sucking  all  their  lives,  embraced  so  many  hidden 
points  of  beauty.  I  spent  a  very  pleasant  hour  with 
these  young  philosophers ;  and  at  the  end  of  the  lesson 
emptied  my  pockets  among  the  class,  and  permitted  them 
to  experiment  upon  the  sugar-candy  in  the  way  usual 
to  boys. 

I  know  not  whether  this  great  assembly  will  deem  it 


CRYSTALS   AND   MOLECULAR   FORCE.  505 

an  impertinence  on  my  part  if  I  seek  to  instruct  them,  for 
an  hour  or  so,  on  the  subject  chosen  for  my  class.  In 
doing  so  I  run  the  imminent  risk  of  being  wearisome  as 
well  as  impertinent ;  while  labouring  under  the  further 
disadvantage  of  not  being  able  to  make  matters  pleasant 
at  the  conclusion  of  the  lecture,  by  the  process  adopted  at 
the  end  of  my  lesson  to  the  boys.  The  experiment,  how- 
ever, must  be  made. 

We  are  to  consider  this  evening  some  of  the  phe- 
nomena of  Crystallisation ;  but  in  order  to  trace  the 
genesis  of  the  notions  now  entertained  upon  the  subject, 
we  have  to  go  a  long  way  back.  In  the  drawing  of  a  bow, 
the  darting  of  a  javelin,  the  throwing  of  a  stone — in  the 
lifting  of  burdens,  and  in  personal  combats,  even  savage 
man  became  acquainted  with  the  operation  of  force.  His 
first  efforts  were  directed  towards  securing  food  and 
shelter  ;  but  ages  of  discipline,  during  which  his  power 
was  directed  against  nature,  against  his  prey,  and  against 
his  fellow-man,  taught  him  foresight.  He  laid  by  at 
the  proper  season  stores  of  food,  thus  obtaining  time  to 
look  about  him,  and  to  become  an  observer  and  enquirer. 
He  discovered  two  things,  which  must  have  profoundly 
stirred  his  curiosity,  and  sent  down  to  us  the  record  of 
his  discovery.  He  found  that  a  kind  of  resin  dropped 
from  a  certain  tree  possessed,  when  rubbed,  the  power 
of  drawing  light  bodies  to  itself,  and  of  causing  them  to 
cling  to  it;  and  he  also  found  that  a  particular  stone 
exerted  a  similar  power  over  a  particular  kind  of 
metal.  I  allude,  of  course,  to  electrified  amber,  and  to 
the  loadstone,  or  natural  magnet,  and  its  power  to  attract 
particles  of  iron.  Previous  experience  had  enabled  our 
early  enquirer  to  distinguish  between  a  push  and  a  pull. 
In  fact,  muscular  efforts  might  be  divided  into  pushes 
and  pulls.  Augmented  experience  showed  him  that  in 
the  case  of  the  magnet  and  the  amber,  pulls  and  pushes-- 


6«6  FRAGMENTS   OF   SCIENCE. 

attractions  and  repulsions — were  also  exerted  ;  and,  by  a 
kind  of  poetic  transfer,  he  applied  to  things  external 
to  himself,  the  conceptions  derived  from  the  exercise  of 
his  own  muscular  power.  The  magnet  and  the  rubbed 
amber  also  pushed  and  pulled,  or,  in  other  words,  exerted 
force. 

In  the  time  of  the  great  Lord  Bacon  the  margin  of 
these  pushes  and  pulls  was  vastly  extended  by  Dr.  Gil- 
bert, a  man  probably  of  firmer  fibre,  and  of  finer  insight, 
than  Bacon  himself.  He,  moreover,  was  one  of  the 
earliest  to  enter  upon  that  career  of  severe  experimental 
research,  which  has  rendered  physical  science  almost  as 
stable  as  the  system  of  nature  which  it  professes  to  ex- 
plain. Gilbert  proved  that  a  multitude  of  other  bodies, 
when  rubbed,  exerted  the  power  which,  thousands  of  years 
previously,  had  been  observed  in  amber.  In  this  way  the 
notion  of  attraction  and  repulsion  in  external  nature  was 
rendered  familiar.  It  was  a  matter  of  experience  that 
bodies,  between  which  no  visible  link  or  connection 
existed,  possessed  the  power  of  acting  upon  each  other ; 
and  the  action  came  to  be  technically  called  *  action  at  a 
distance.' 

But  out  of  experience  in  science  there  always  grows 
something  finer  than  mere  experience.  Experience,  in 
fact,  only  furnishes  the  soil  for  plants  of  higher  growth ; 
and  this  observation  of  action  at  a  distance  furnished 
material  for  speculation  upon  the  largest  of  problems. 
Bodies  were  observed  to  fall  to  the  earth.  Why  should 
they  do  so  ?  The  earth  was  proved  to  revolve  round  the 
sun ;  and  the  moon  to  revolve  round  the  earth.  Why 
should  they  do  so?  What  prevents  them  from  flying 
straight  off  into  space  ?  Supposing  it  to  be  ascertained 
that  from  a  part  of  the  earth's  rocky  crust  a  firmly-fixed 
and  tightly-stretched  chain  started  towards  the  sun,  we 
might  be  inclined  to  conclude  that  the  earth  is  held  in  its 


CRYSTALS   AND    MOLECULAR  FORCE.  667 

orbit  by  the  chain — that  the  sun  twirls  the  earth  around 
him,  as  a  boy  twirls  round  his  head  a  bullet  at  the  end  of 
a  string.  But  why  should  the  chain  be  needed  ?  asks  the 
speculative  mind.  It  is  a  fact  of  experience  that  bodies 
can  attract  each  other  at  a  distance,  without  the  in- 
tervention of  any  chain.  Why  should  not  the  sun  and 
earth  so  attract  each  other  ?  and  why  should  not  the  fall 
of  bodies  from  a  height  be  the  result  of  their  attraction 
by  the  earth  ?  Here  then  we  have  one  of  those  higher 
thoughts  of  speculation,  which  grow  out  of  the  fruitful 
soil  of  observation.  Having  started  with  the  savage,  and 
his  sensations  of  muscular  force,  we  pass  on  to  the  obser- 
vation of  force  exerted  between  a  magnet  and  rubbed 
amber,  and  the  bodies  which  they  attract,  rising,  by  an 
unbroken  growth  of  ideas,  to  a  conception  of  the  force  by 
which  sun  and  planets  are  held  together. 

This  idea  of  attraction  between  sun  and  planets  had 
become  familiar  in  the  time  of  Newton.  He  set  himself 
to  examine  the  attraction ;  and  here,  as  elsewhere,  we 
find  the  speculative  mind  falling  back  for  its  materials 
upon  experience.  It  had  been  observed,  in  the  case  of 
magnetic  and  electric  bodies,  that  the  nearer  they  were 
brought  together  the  stronger  was  the  force  exerted  be- 
tween them ;  while,  by  increasing  the  distance,  the  force 
diminished  until  it  became  insensible.  Hence  the  infer- 
ence that  the  assumed  pull  between  the  earth  and  the 
sun  would  be  influenced  by  their  distance  asunder. 
Guesses  had  been  made  as  to  the  exact  manner  in  which 
the  force  varied  with  the  distance;  but,  in  the  case  of 
Newton,  the  guess  was  supplemented  by  being  brought 
to  the  severe  test  of  experiment  and  calculation.  Com- 
paring the  pull  of  the  earth  upon  a  body  close  to  its 
surface,  with  the  pull  upon  the  moon,  240,000  miles 
away,  Newton  rigidly  established  the  law  of  variation 
with  the  distance,  thus  placing  in  our  hands  a  principle 


568  FRAGMENTS   OF   SCIENCE. 

which  enables  us  to  determine  the  date  of  astronomical 
events  in  the  far  historic  past,  or  in  the  distant  future.1 

But  on  his  way  to  this  great  result  Newton  found  room 
in  his  ample  mind  for  other  conceptions,  some  of  which, 
indeed,  constituted  the  necessary  stepping-stones  to  his 
result.  The  one  which  here  concerns  us  most  is  this : 
according  to  Newton  not  only  does  the  sun  attract  the 
earth,  and  the  earth  attract  the  sun,  as  wholes,  but  every 
particle  of  the  sun  attracts  every  particle  of  the  earth, 
and  the  reverse.  His  conclusion  was,  that  the  attraction 
of  the  masses  was  simply  the  sum  of  the  attractions  of 
their  constituent  particles. 

This  result  seems  so  obvious  that  you  will  perhaps 
wonder  at  my  dwelling  upon  it ;  but  it  really  marks  a 
turning  point  in  our  notions  of  force.  You  have  probably 
heard  of  late  of  certain  disturbers  of  the  public  peace 
named  Democritus,  Epicurus,  and  Lucretius.  These  men 
adopted,  developed,  and  diffused  the  dangerous  doctrine 
of  atoms  and  molecules,  which  found  its  consummation  in 
this  city  of  Manchester  at  the  hands  of  the  immortal  John 
Dalton.  Now,  the  grand  old  Pagans  whom  I  have  named, 
and  their  followers,  up  to  the  time  of  Newton,  had  pictured 
their  atoms  as  falling  and  flying  through  space,  hitting 
each  other,  and  clinging  together  by  imaginary  hooks  and 
claws.  They  entirely  missed  the  central  idea  that  the 
atoms  and  molecules  could  come  together,  not  by  being 
fortuitously  knocked  against  each  other,  but  by  their  own 
mutual  attractions.  This  is  one  of  the  great  steps  taken 
by  Newton.  He  familiarised  the  world  with  the  concep- 
tion of  molecular  force. 

In  the  case  of  electricity  and  magnetism,  a  double  exer- 
cise of  force  had  been  observed — repulsion  had  been  always 
seen  to  accompany  attraction.  Electricity  and  magnetism 

:  See  pp.  396,  397,  398. 


CRYSTALS   AND   MOLECULAR   FORCE.  6G9 

were  examples  of  what  are  called  polar  forces  ;  and  in 
the  case  of  magnetism,  experience  itself  pushed  the  mind 
irresistibly  beyond  the  bounds  of  experience,  compelling 
it  to  conclude  that  the  polarity  of  the  magnet  was  resi- 
dent in  its  molecules.  I  hold  a  strip  of  steel  by  its  centre, 
between  my  finger  and  thumb.  One  half  of  the  strip 
attracts,  and  the  other  half  repels,  the  north  end  of  a 
magnetic  needle.  I  break  the  strip  in  the  middle,  and 
what  occurs  ?  The  middle  point  or  equator  of  the  mag- 
net has  shifted  to  the  centre  of  the  new  strip.  This 
half,  which  a  moment  ago  attracted  throughout  its  entire 
length  the  north  pole  of  a  magnetic  needle,  is  now 
divided  into  two  new  halves,  one  of  which  wholly  attracts, 
and  the  other  of  which  wholly  repels,  the  north  pole  of 
the  needle.  Thus  the  half,  when  broken  off,  proves  to  be 
as  perfect  a  magnet  as  the  whole.  You  may  break  this 
half,  and  go  on  till  further  breaking  becomes  impossible 
through  the  very  smallness  of  the  fragments;  still  you 
find  at  the  end  that  the  smallest  fragment  is  endowed 
with  two  poles,  and  is,  therefore,  a  perfect  magnet.  But 
you  cannot  stop  here :  you  imagine  where  you  cannot 
experiment ;  and  reach  the  conclusion  entertained  by  all 
scientific  men,  that  the  magnet  which  you  can  see  and 
feel  is  an  assemblage  of  molecular  magnets  which  you 
cannot  see  and  feel,  but  which  must  be  intellectually 
discerned. 

In  this  power  of  ideal  extension  consists  for  the  most 
part  the  difference  between  great  and  mediocre  investi- 
gators. The  man  who  cannot  break  the  bounds  of  expe- 
rience, but  holds  on  to  the  region  of  sensible  facts,  may 
be  an  excellent  observer,  but  he  is  no  philosopher,  and 
can  never  reach  those  principles  which  render  the  facts 
of  science  organic.  True,  the  speculative  faculty  may  be 
abused  like  all  good  things,  but  it  is  not  men  of  science 
that  are  most  likely  to  abuse  it.  When,  more  than 


570  FKAGMENTS   OF  SCIENCE. 

thirty  years  ago,  a  townsman  of  your  own  accounted  for 
the  heat  of  chemical  combination  by  referring  it  to  the 
clash  of  atoms  falling  together,  he  described  an  image 
presented  to  his  mind,  but  entirely  beyond  the  reach  of 
his  senses.  It  was,  however,  an  image  out  of  which  grew 
memorable  consequences;  among  others  this  one  of  a 
personal  nature.  The  walls  of  this  Free  Trade  Hall,  or 
rather  its  predecessor,  have  rung  with  the  speeches  of 
Cobden,  and  Bright,  and  Wilson.  But  at  the  time  when 
their  words  rolled  round  the  world,  the  enquirer  to 
whom  I  have  referred  was  silently  and  studiously  engaged 
in  your  city,  grappling  with  the  problem  of  heat  and 
work,  and  by  implication  with  far  higher  problems.  He 
grappled  with  it  successfully,  bringing  it  into  the  full 
light  of  experimental  demonstration.  And  I  venture  to 
affirm  that  in  the  coming  time,  not  even  the  great  orators 
and  politicians  just  named,  not  even  the  greatest  of  your 
manufacturing  princes,  will  enjoy  a  purer,  a  more  perma- 
nent or  enviable  fame — there  is  not  a  man  amongst  them 
of  whom  Manchester  will  be  more  justly  proud,  than  of 
James  Prescott  Joule,  her  modest  brewer,  but  renowned 
scientific  worker. 

We  have  now  to  track  still  further  the  growth  of  our 
notions  of  force.  We  have  learned  that  magnetism  is 
a  polar  force ;  and  experience  hints  that  a  force  of  this 
kind  may  exert  a  certain  structural  power.  It  is  known, 
for  example,  that  iron  filings  strewn  round  a  magnet 
arrange  themselves  in  definite  lines,  called,  by  some, 
'  magnetic  curves,'  and,  by  Faraday,  '  lines  of  magnetic 
force.'  In  these  observed  results  of  magnetic  polarity 
we  find  the  material  for  speculation,  in  an  apparently 
distant  field.  You  can  readily  make  an  experiment  or 
two  for  yourselves  with  any  magnet.  Over  two  magnets 
now  before  me,  is  spread  a  sheet  of  paper.  Scattering 
iron  filings  over  the  paper,  and  tapping  it,  the  filings 


CRYSTALS  AND   MOLECULAR  FORCE.  571 

arrange  themselves  in  a  singular  manner.  Polar  force  is 
here  in  action,  and  every  particle  of  the  iron  responds  to 
that  force.  The  consequence  is  a  certain  structural 
arrangement,  a  kind  of  architectural  effort — if  I  may  use 
the  term — on  the  part  of  the  iron  filings.  Here  is  a  fact 
of  experience  which,  as  you  will  see  immediately,  furnishes 
further  material  for  the  mind  to  operate  upon,  rendering 
it  possible  to  attain  intellectual  clearness  and  repose,  while 
speculating  upon  apparently  remote  phenomena. 

You  cannot  enter  a  quarry  and  scrutinise  the  texture 
of  the  rocks  without  seeing  that  it  is  not  perfectly  homo- 
geneous. If  the  quarry  be  of  granite,  you  find  the  rocks 
to  be  an  agglomeration  of  crystals  of  quartz,  mica,  and 
felspar.  If  the  rocks  be  sedimentary,  you  find  them,  for 
the  most  part,  composed  of  crystalline  particles  derived 
from  older  rocks.  If  the  quarry  be  marble,  you  find  the 
fracture  of  the  rocks,  to  be  what  is  called  crystalline 
fracture.  These  crystals  are,  in  fact,  everywhere.  If 
you  break  a  sugar-loaf,  you  find  the  surface  of  fracture 
to  be  composed  of  small,  shining,  crystalline  surfaces. 
In  the  fracture  of  cast  iron  you  notice  the  same  thing ; 
and  next  to  his  great  object  of  squeezing  out  the  en- 
tangled gas  from  his  molten  metal,  another  object  of  your 
celebrated  townsman,  Sir  Joseph  Whitworth,  when  he 
subsequently  kneads  his  masses  of  white-hot  steel,  as  if 
they  were  so  much  dough,  is  to  abolish  this  crystalline 
structure.  The  shining  surfaces  observed  in  the  case  of 
crystalline  fracture  are  surfaces  of  weak  cohesion ;  and 
when  you  come  to  examine  large  and  well-developed 
crystals,  you  soon  learn  why  they  are  so.  With  the 
edge  of  my  knife  I  try,  in  various  directions,  the  crystal 
of  sugar,  referred  to  at  the  beginning  of  this  lecture, 
and  find  it  obdurate ;  but  I  at  length  come  upon  a  direc- 
tion in  which  it  splits  cleanly  before  the  knife,  revealing 
two  shining  surfaces  of  cleavage.  Such  surfaces  are  se^n 


572  FRAGMENTS   OP   SCIENCE. 

when  you  break  cast  iron,  and  the  metal  is  strengthened 
by  their  abolition.  Other  crystals  split  far  more  easily 
than  sugar. 

In  the  course  of  scientific  investigation,  then,  as  I 
have  tried  to  impress  upon  you,  we  make  continual  iu- 
cursions  from  a  physical  world,  where  we  observe  facts, 
into  a  super-  or  sub-physical  world,  where  the  facts  elude 
all  observation,  and  we  are  thrown  back  upon  the  pic- 
turing power  of  the  mind.  By  the  agreement  or  disagree- 
ment of  our  picture  with  subsequent  observation  it  must 
stand  or  fall.  If  it  represent  a  reality,  it  abides  with  us; 
if  not,  it  fades  like  an  unfixed  photograph  in  the  presence 
of  subsequent  light.  Let  me  illustrate  this.  You  know 
how  very  easy  it  is  to  cleave  slate  rock.  You  know  that 
Snowdon,  Honister  Crag,  and  other  hills  of  Wales  and 
Cumberland,  may  be  thus  cloven  from  crown  to  base. 
How  was  the  cleavage  produced  ?  By  simple  bedding  01 
stratification,  you  may  answer.  But  the  answer  would  not 
be  correct;  for,  as  Henslow  and  Sedgwick  showed,  the 
cleavage  often  cuts  the  bedding  at  a  high  angle.  Well, 
here,  as  in  other  cases,  the  mind,  endeavouring  to  find  a 
cause,  passed  from  the  world  of  fact  to  the  world  of  imagi- 
nation, and  it  was  assumed  that  slaty  cleavage,  like  crystal- 
line cleavage,  was  produced  by  polar  force.  And,  indeed, 
an  interesting  experiment  of  Mr.  Justice  Grove  could  be 
called  upon  to  support  this  view.  I  have  here,  in  a  cylin- 
der with  glass  ends,  a  fine  magnetic  mud,  consisting  of 
small  particles  of  oxide  of  iron  suspended  in  water.  You 
can  render  those  suspended  particles  polar  by  sending 
round  the  cylinder  an  electric  current ;  and  one  striking 
consequence  of  this  action  may  be  rendered  evident.  At 
present  the  particles  are  promiscuously  strewn  in  the 
liquid,  and  the  strongest  beam  of  light  can  hardly  struggle 
through  the  turbid  medium.  But  when  the  current  passes 
they  all  set  their  lengths  parallel  to  the  axis  of  the 


CRYSTALS  AND   MOLECULAR  FORCE.  673 

cylinder,  and  light  immediately  flashes  out  upon  the 
screen.  Now,  if  you  imagine  the  mud  of  slate  rocks  to 
have  been  thus  acted  on,  so  as  to  place  its  particles  with 
their  lengths  in  a  common  direction,  such  elongated  and 
flat  particles  would,  when  solidified,  certainly  produce  a 
cleavage. 

Here  we  have  a  sample  of  the  'fading  photograph ' ; 
for,  plausible  as  this  is,  it  is  not  the  proper  explanation, 
the  cleavage  of  the  slate  rocks  being  demonstrably  not 
crystalline,  but,  as  shown  by  Sharpe,  Sorby,  Haughton, 
and  myself,  due  to  pressure. 

The  outward  forms  of  crystals  are  various  and  beautiful. 
A  quartz-crystal,  for  example,  is  a  six-sided  prism,  capped 
at  each  end  by  six-sided  pyramids.  Eock-salt,  with 
which  your  neighbours  in  Cheshire  are  so  well  acquainted, 
crystallises  in  cubes  ;  and  it  can  be  cloven  into  cubes 
until  you  cease  to  be  able  to  cleave  further  for  the 
very  smalmess  of  the  masses.  Eock-salt  is  thus  proved 
to  have  three  planes  of  cleavage,  at  right  angles  to  each 
other.  Iceland  spar  has  also  three  planes  of  cleavage, 
but  they  are  oblique  instead  of  rectangular,  the  crystal 
being,  therefore,  a  rhomb  instead  of  a  cube.  Various  crys- 
tals, moreover,  cleave  with  different  facilities  in  different 
directions.  A  plane  of  '  principal  cleavage '  exists  in  these 
crystals,  and  it  is  accompanied  by  other  planes,  sometimes 
of  equal,  sometimes  of  unequal,  value  as  regards  ease  ot 
cleavage.  Heavy  spar,  for  example,  cleaves  into  prisms, 
with  a  rhombus  or  diamond-shaped  figure  for  a  base.  It 
cleaves  with  greatest  ease  across  the  axis  of  the  prism, 
the  other  two  cleavages  having  equal  values.  Selenite 
cleaves  with  extreme  facility  in  one  direction,  and  with 
unequal  facilities  in  two  other  directions. 

Looking  at  these  beautiful  edifices  and  their  internal 
structure,  the  pondering  mind  has  forced  upon  it  the  ques- 
tion, How  have  these  crystals  been  built  up  ?  What  is 


574  FKAGMENTS   OF   SCIENCE. 

tne  origin  of  this  crystalline  architecture?  Without 
crossing  the  boundary  of  experience,  we  can  make  no 
attempt  to  answer  this  question.  \Ve  have  obtained  clear 
conceptions  of  polar  force  :  we  know  that  polar  force  may 
be  resident  in  the  molecules,  or  smallest  particles  of  matter, 
and  that  by  the  play  of  this  force  structural  arrangement 
is  possible.  What,  in  relation  to  our  present  question,  is 
the  natural  action  of  a  mind  furnished  with  this  know- 
ledge ?  Why,  it  is  compelled  by  its  bias  towards  unity  of 
principle  to  transcend  experience,  and  endow  the  atoms 
and  molecules  of  which  these  crystals  are  built  with 
definite  poles,  whence  issue  attractions  and  repulsions  for 
other  poles.  In  virtue  of  these  attractions  and  repulsions 
some  poles  are  drawn  together,  some  retreat  from  each 
other ;  atom  is  thus  added  to  atom,  and  molecule  to  mole- 
cule, not  boisterously  or  fortuitously,  but  silently  and 
symmetrically,  and  in  accordance  with  laws  more  rigid 
than  those  which  guide  a  human  builder  when  he  places 
his  bricks  and  stones  together.  From  this  play  of  invi- 
sible particles  we  see  finally  growing  up  before  our  eyes 
these  exquisite  structures,  to  which  we  give  the  name  of 


In  the  specimens  hitherto  placed  before  you  the  work 
of  the  atomic  architect  has  been  completed  ;  but  you  shall 
see  him  immediately  at  work.  In  the  first  place,  however, 
I  will  try  to  pull  to  pieces  before  your  eyes  one  of  his  most 
familiar  edifices,  ordinary  ice.  The  agent  to  be  employed 
in  taking  down  the  molecules  of  the  ice  is  a  suitably 
concentrated  beam  of  heat.  Sent  skilfully  through  the 
crystal,  the  beam  selects  certain  points  for  attack  ;  round 
about  those  points  it  works  silently,  undoing  the  crystal- 
line architecture,  and  reducing  to  the  freedom  of  liquidity 
molecules  which  had  been  previously  locked  in  a  solid 
embrace.  The  liquefied  spaces  are  rendered  visible  by 
strong  illumination.  Bound  numerous  points  in  the  ice 


CRYSTALS   AND   MOLECULAR  FORCE.  675 

we  see  expanding  liquid  flowers,  each  with  six  petals,  and 
a  central  vacuous  spot.  They  grow  larger  and  larger, 
assuming,  as  they  do  so,  beautifully  crimped  borders ;  and 
showing,  if  I  might  use  such  terms,  the  pains,  and  skill, 
and  exquisite  sense  of  the  beautiful,  displayed  by  nature 
in  the  formation  of  a  common  block  of  ice. 

Here  we  have  before  us  a  process  of  demolition,  which 
clearly  reveals  the  reverse  process  of  erection.  I  wish, 
however,  to  show  you  the  molecules  in  the  act  of  following 
their  architectural  instincts,  and  building  themselves 
together.  You  know  how  alum,  and  nitre,  and  sugar  crys- 
tals are  formed.  The  substance  to  be  crystallised  is 
dissolved  in  a  liquid,  and  the  liquid  is  permitted  to  evapo- 
rate. The  solution  soon  becomes  supersaturated,  for  none 
of  the  solid  is  carried  away  by  evaporation  ;  and  then  the 
molecules,  no  longer  able  to  enjoy  the  freedom  of  liquidity, 
close  up  together  and  form  crystals.  My  object  now  is  to 
make  this  process  rapid  enough  to  enable  you  to  see  it, 
and  still  not  too  rapid  to  be  followed  by  the  eye.  For 
this  purpose  a  powerful  solar  microscope  and  an  intense 
source  of  light  are  needed.  They  are  both  here.  Pouring 
over  a  clean  plate  of  glass  a  solution  of  sal-ammoniac,  and 
placing  the  glass  on  its  edge,  the  excess  of  the  liquid  flows 
away,  but  a  film  clings  to  the  glass.  The  beam  employed 
to  illuminate  this  film  hastens  its  evaporation,  and  brings 
it  rapidly  into  a  state  of  supersaturation ;  and  now  you  see 
the  orderly  progress  of  the  crystallisation  over  the  entire 
screen.  You  may  produce  something  similar  to  this  if 
you  breathe  upon  the  frost  ferns  which  overspread  your 
window-panes  in  winter,  and  permit  the  liquid  to  re- 
crystallise.  It  runs,  as  if  alive,  into  the  most  beautiful 
forms. 

In  this  case  the  crystallising  force  is  hampered  by  the 
adhesion  of  the  liquid  to  the  glass  ;  nevertheless  the  play 
of  power  is  strikingly  beautiful.  In  the  next  example  our 


676  FRAGMENTS   OF   SCIENCE. 

crystals  will  not  be  so  much  troubled  by  adhesion,  for  we 
shall  liberate  the  atoms  at  a  distance  from  the  surface  of 
the  glass.  Sending  an  electric  current  through  water,  we 
decompose  the  liquid,  and  the  bubbles  of  the  constituent 
gases  rise  before  your  eyes.  Sending  the  same  current 
through  a  solution  of  acetate  of  lead,  the  lead  is  liberated, 
and  its  free  atoms  build  themselves  into  crystals  of  mar- 
vellous beauty.  They  grow  before  you  like  sprouting 
ferns,  exhibiting  forms  as  wonderful  as  if  they  had  been 
produced  by  the  play  of  vitality  itself.  Nitrate  of  silver, 
thus  decomposed,  produces  silver  trees  of  extraordinary 
beauty.  The  mechanism  of  the  process  is  rendered  intelli- 
gible by  the  picture  of  atomic  poles ;  but  there  is  some- 
thing here  incipient,  which  the  mind  of  man  has  never 
yet  seized ;  and  which,  so  far  as  research  has  penetrated, 
is  found  indissolubly  joined  with  what  we  despise  as  matter. 
I  have  seen  these  things  hundreds  of  times,  but  never 
without  wonder.  And  perhaps  you  would  allow  me  a 
moment's  diversion  from  my  subject,  to  say  that  often 
in  the  spring-time,  when  looking  with  delight  on  the 
sprouting  foliage,  *  considering '  the  lilies  of  the  field,  and 
sharing  the  general  joy  of  opening  life,  I  have  asked 
myself  whether  there  is  no  power,  being,  or  tiling,  in 
the  universe,  whose  knowledge  of  that  of  which  I  am  so 
ignorant  is  greater  than  mine.  I  have  said  to  myself,  Can 
man's  knowledge  be  the  greatest  knowledge — and  man's 
life  the  highest  life  ?  l  My  friends,  the  profession  of  that 
Atheism  with  which  I  am  sometimes  so  lightly  charged 
would,  in  my  case,  be  an  impossible  answer  to  this  ques- 
tion :  only  slightly  preferable  to  that  fierce  and  distorted 
Theism  which  still  reigns  rampant  in  some  minds,  as  the 
survival  of  a  more  ferocious  age. 

In  the  formation  of  our  lead  and  silver  trees,  we  needed 
1  An  old  reflection  of  mine,  see  p.  458. 


CRYSTALS  AND   MOLECULAR    FORCE.  577 

an  agent  to  wrest  the  lead  and  the  silver  from  the  acids 
with  which  they  were  combined.  A  similar  agent  is 
required  in  the  vegetable  world.  The  solid  matter  of 
our  metallic  trees  was,  in  the  first  instance,  disguised  in  a 
transparent  liquid;  the  solid  matter  of  our  woods  and 
forests  is  also,  for  the  most  part,  disguised  in  a  transparent 
gas,  formed  by  the  union  of  carbon  and  oxygen,  and 
diffused  in  small  quantities  in  the  atmosphere.  Subjected 
to  an  action  somewhat  analogous  to  that  of  the  electric 
current,  in  the  case  of  our  lead  and  silver  solutions,  this 
gas  has  its  carbon  liberated  and  deposited  as  woody  fibre.* 
The  aqueous  vapour  of  the  air,  subjected  to  a  similar 
action,  has  its  hydrogen  liberated  from  its  oxygen,  the 
former,  like  the  carbon,  entering  the  tissue  of  the  tree. 
But  what  is  it  in  nature  that  plays  the  part  of  the  electric 
current  in  our  experiments  ?  The  light-waves  of  the  sun. 
The  leaves  of  plants  absorb  both  the  carbonic  acid  and  the 
aqueous  vapour  of  the  air.  In  the  leaves,  the  solar  rays 
decompose  the  acid  and  the  water,  permitting  the  oxygen, 
in  both  cases,  to  escape  into  the  air,  and  allowing  the 
carbon  and  the  hydrogen  to  follow  the  bent  of  their  own 
structural  forces.  And  just  as  the  molecular  attractions 
of  the  silver  and  the  lead  found  expression  in  the  pro- 
duction of  those  beautiful  branching  forms,  seen  in  our 
experiments,  so  do  the  molecular  attractions  of  the  libe- 
rated carbon  and  hydrogen  find  expression  in  the  architec- 
ture of  grasses,  plants,  and  trees. 

In  the  fall  of  a  cataract  and  in  the  rush  of  the  wind 
we  have  examples  of  mechanical  power.  In  the  combina- 
tions of  chemistry,  and  in  the  formation  of  crystals  and 
vegetables,  we  have  examples  of  molecular  power,  which 
may  be  turned  to  mechanical  account.  As  regards  our 
store  of  the  latter,  the  world  may  be  divided  into  two 
kinds  of  matter ;  or  rather  the  matter  of  the  world  may 


678  FRAGMENTS   OF   SCIENCE. 

be  classified  under  two  distinct  heads — namely,  atoms  and 
molecules  which  have  already  rushed  together  and  satisfied 
their  mutual  attractions,  and  atoms  and  molecules  whose 
attractions  are,  as  yet,  unsatisfied.  With  regard  to 
motive  power,  the  working  of  machinery,  or  the  per- 
formance of  mechanical  work  generally,  by  means  of  the 
materials  of  the  earth's  crust,  we  are  entirely  dependent 
on  those  atoms  and  molecules  whose  attractions  are  as 
yet  unsatisfied.  These  can  produce  motion,  and  it  is 
this  molecular  motion  that  we  utilise  in  our  machines. 
We  can  get  power  out  of  oxygen  and  hydrogen,  during 
the  act  of  their  union,  but  when  they  are  combined, 
and  when  the  motion  consequent  on  their  combina- 
tion has  been  expended,  no  further  power  can  be  got  out 
of  them.  As  dynamic  agents  they  are  dead.  When  we 
examine  the  materials  of  the  earth's  crust,  we  find  them 
consisting  for  the  most  part  of  substances  whose  atoms 
have  already  closed  in  chemical  union — whose  mutual 
attractions  are  satisfied.  Granite,  for  instance,  is  a  widely- 
diffused  substance ;  but  granite  consists,  in  great  part,  of 
silicon,  oxygen,  potassium,  calcium,  and  aluminium,  whose 
atoms  met  long  ago  in  chemical  combination,  and  are 
therefore  dead.  Limestone  is  also  a  widely-diffused  sub- 
stance. It  is  composed  of  carbon,  oxygen,  and  a  metal 
called  calcium.  But  the  atoms  of  those  substances  closed 
long  ago  in  chemical  union,  and  are  therefore  eternally  at 
rest. 

In  this  way  we  might  go  over  the  whole  of  the 
materials  of  the  earth's  crust,  and  satisfy  ourselves  that 
though  they  were  sources  of  power  in  ages  past,  and  long 
before  any  being  had  appeared  on  the  surface  of  the  earth 
capable  of  turning  their  energies  to  account,  they  are  not 
sources  of  power  now.  And  here  we  might  halt  for  a 
moment  to  remark  on  that  tendency,  so  prevalent  in  the 
world,  to  regard  everything  as  made  for  human  use. 


CRYSTALS   AND   MOLECULAR   FORCE.  679 

Those  who  entertain  this  notion  hold,  I  think,  an  over- 
weening opinion  of  their  own  importance  in  the  system  of 
nature.  Flowers  bloomed  before  men  saw  them,  and  the 
quantity  of  energy  wasted  before  man  could  utilise  it,  is 
all  but  infinite  compared  with  what  now  remains  to  be 
applied.  We  are  truly  heirs  of  all  the  ages;  but,  as 
honest  men,  it  behoves  us  to  know  the  extent  of  our 
inheritance ;  and,  as  brave  ones,  not  to  whimper,  if  it 
should  prove  to  be  less  than  we  supposed.  Inordinate 
claims  and  expectations  are  not  necessary  to  the  moulding 
of  healthy,  happy,  and  patriotic  men.  Not  with  beggarly 
fear,  or  mutinous  discontent,  but  rather  with  elation  of 
mind,  ought  we  to  accept  the  brotherhood  affirmed  by  the 
puet,  when  asked  the  use  of  the  beautiful  rhodora — 

Why  thou  wert  there,  0  rival  of  the  rose ! 

I  never  thought  to  ask,  I  never  knew, 

But  in  my  simple  ignorance  suppose 

The  self-same  Power  that  brought  me  here  brought  you.1 

A  few  exceptions  to  the  general  state  of  union  of  the 
particles  of  the  earth's  crust — vast,  in  relation  to  us,  but 
trivial  in  comparison  to  the  total  store  of  which  they  are 
the  residue — still  remain.  They  constitute  our  main 
sources  of  motive  power.  By  far  the  most  important  of 
these  are  our  beds  of  coal.  Distance  still  intervenes 
between  the  atoms  of  carbon  and  those  of  atmospheric 
oxygen,  across  which  the  atoms  may  be  urged  by  their 
mutual  attractions  ;  and  we  can  utilise  the  motion  thus 
produced.  Once  the  carbon  and  the  oxygen  have  rushed 
together,  so  as  to  form  carbonic  acid,  their  mutual  attrac- 
tions are  satisfied ;  and,  while  they  continue  in  this  con- 
dition, as  dynamic  agents  they  are  dead.  A  pound  of 
coal  produces  by  its  combination  with  oxygen  an  amount 
of  heat  which,  if  mechanically  applied,  would  raise  a 
weight  of  a  ton  to  a  height  of  about  a  mile  above  the 

1  Emerson. 
27 


6«0  FRAGMENTS   OP   SCIENCE. 

earth's  surface.  Conversely,  a  ton  falling  from  the  height 
of  a  mile,  and  striking  against  the  earth,  would  generate 
an  amount  of  heat  equal  to  that  developed  by  the  com- 
bustion of  a  pound  of  coal.  Consider,  then,  the  enormous 
energies  of  our  coal-fields.  We  dig  annually  from  our 
pits  about  100  millions  of  tons  of  coal,  the  combus- 
tion of  a  single  pound  of  which,  supposing  it  to  take 
place  in  a  minute,  would  be  equivalent  to  the  work  of  300 
horses.  If  we  suppose  120  millions  of  horses  working  day 
and  night  with  unimpaired  strength  for  a  year,  their 
united  energies  would  enable  them  to  perform  an  amount 
of  work  just  equivalent  to  the  annual  produce  of  our  coal- 
fields. Our  woods  and  forests  are  also  sources  of  mecha- 
nical energy,  because  they  have  the  power  of  uniting  with 
the  atmospheric  oxygen.  Passing  from  plants  to  animals, 
we  find  that  the  source  of  motive  power  just  referred 
to  is  also  the  source  of  muscular  power.  A  horse  can 
perform  work,  and  so  can  a  man ;  but  this  work  is  at 
bottom  the  molecular  work  of  the  elements  of  the  food  and 
the  oxygen  of  the  air.  We  inhale  this  vital  gas.  and  bring 
it  into  sufficiently  close  proximity  with  the  carbon  and  the 
hydrogen  of  the  food.  These  unite  in  obedience  to  their 
mutual  attractions ;  and  their  motion  towards  each  other, 
properly  turned  to  account  by  the  wonderful  mechanism  of 
the  body,  becomes  muscular  motion. 

Wherever  work  is  done  by  heat,  heat  disappear?.  The 
quantity  of  heat  communicated  to  the  boiler  of  a  working 
steam-engine  is  greater  than  that  obtainable  from  the 
recondensation  of  the  steam  after  it  has  done  its  work ; 
and  the  amount  of  work  performed  is  the  exact  equivalent 
of  the  missing  amount  of  heat.  One  fundamental  thought 
pervades  all  sxich  statements :  there  is  one  tap  root  from 
which  they  all  spring.  This  is  the  ancient  maxim  that 
out  of  nothing  nothing  comes  ;  that  neither  in  the  organic 
world  nor  in  the  inorganic  is  power  produced  without 


CRYSTALS  AND   MOLECULAR  FORCE.  681 

the  expenditure  of  other  power ;  that  neither  in  the  plant 
nor  in  the  animal  is  there  a  creation  of  force  or  motion. 
Trees  grow,  and  so  do  men  and  horses ;  and  here  we  have 
new  power  incessantly  introduced  upon  the  earth.  But 
its  source,  as  I  have  already  stated,  is  the  sun.  For  it 
is  the  sun  that  separates  the  carbon  from  the  oxygen  of 
the  carbonic  acid,  and  enables  them  to  recx>mbine.  And 
whether  they  recombine  in  the  furnace  of  the  steam- 
engine,  or  in  the  animal  body,  the  origin  of  their  power  is 
the  same.  In  this  sense  we  are  all  '  souls  of  fire  and 
children  of  the  sun  ; '  but,  as  remarked  by  Helmholtz,  we 
must  be  content  to  share  our  celestial  pedigree  with  the 
meanest  of  living  things. 

I  look  to  a  still  remoter  brotherhood ;  but  we  are  here 
upon  the  edge  of  a  battlefield  which  I  do  not  intend  to 
enter  to-night ;  from  which,  indeed,  I  have  just  escaped 
bespattered  and  begrimed,  but  without  much  loss  of  heart 
or  hope.  It  only  remains  for  me  to  briefly  indicate  the 
position  of  the  opposing  hosts.  From  the  processes  of  crys- 
tallisation which  you  have  just  seen,  you  may  pass  by 
almost  imperceptible  gradations  to  the  lowest  vegetable 
organisms,  and  from  these  through  higher  ones  up  to  the 
Highest.  The  conflict  referred  to  is :  that  whereas  one 
class  of  thinkers  regard  the  observed  advance  from  the 
crystalline,  through  tho  vegetable  and  animal  worlds,  as 
an  unbroken  process  of  natural  growth,  thus  grasping 
the  world,  inorganic  and  organic,  as  one  vast  and  indis- 
solubly  connected  whole ;  the  other  class  suppose  that  the 
passage  from  the  inorganic  to  the  organic  required  a  dis- 
tinct creative  act,  and  that  to  produce  the  different  forms 
of  organisms,  both  in  the  world  of  fossils  and  in  the  world 
of  living  things,  separate  creative  acts  were  also  needed. 

Which  are  right  and  which  are  wrong  is,  I  submit, 
a  problem  for  reasonable  and  grave  discussion,  and  not 
for  anger  and  hard  names.  The  question  cannot  be  solved 


582  FRAGMENTS   OF   SCIENCE. 

— it  cannot  even  be  shelved — by  angry  abuse.  Nor  can 
it  be  answered  by  appeals  to  hopes  and  fears — to  what 
we  lose  or  gain,  here  or  hereafter,  by  joining  the  one  or 
the  other  side.  The  bribe  of  eternity  itself,  were  it  pos- 
sible to  offer  it,  could  not  prevent  the  human  mind  from 
closing  with  the  truth.  Scepticism  is  at  the  root  of  OUT 
fears.  I  mean  that  scepticism,  which  holds  that  human 
nature,  being  essentially  corrupt  and  vile,  will  go  to  ruin 
if  the  props  of  our  conventional  theology  are  not  main- 
tained. When  I  see  an  able,  and  in  many  respects  a 
courageous,  man,  running  to  and  fro  upon  the  earth,  and 
wringing  his  hands  over  the  threatened  loss  of  his  ideals, 
I  feel  disposed  to  exhort  him  to  cast  out  this  scepticism  ; 
and  to  believe,  undoubtingly,  that  in  the  mind  of  man  we 
have  the  substratum  of  all  ideals.  We  have  there  capacity 
which  will  as  surely  and  infallibly  respond  to  the  utter- 
ances of  a  really  living  soul,  as  string  responds  to  string 
when  the  proper  note  is  sounded.  It  is  the  function  of 
the  teacher  of  humanity  to  call  forth  this  resonance  of  the 
human  heart.  But  the  possibility  of  doing  so  depends 
not  wholly  and  solely  upon  him,  but  upon  the  antecedent 
fact  that  the  conditions  for  its  appearance  are  already 
there. 


Some  of  the  points  referred  to  in  this  fragment  are 
connected  with  their  historic  antecedents  in  the  article 
entitled  'The  Copley  Medallist  for  1871.' 


From  ike  l  Times '  of  November  9,  1874. 

IN  Medicine,  as  elsewhere,  knowledge  grows  and  consolidates 
through  the  conflict  and  sifting  of  opinions  and  evidences.  With 
regard  to  the  great  class  of  diseases  kncwn  as  epidemics,  which 
flourish  through  the  transfer  from  place  to  place,  and  from 
person  to  person,  of  a  something  which  continues  to  exist  through 
its  own  powers  of  reproduction,  physicians  have  long  been 
divided  in  their  notions.  And  with  regard  to  the  title  of  cer- 
tain diseases  to  be  ranked  as  epidemic,  the  opinions  of  the 
medical  world  have  been  equally  divided.  On  this  last  question 
more  especially,  theoretic  notions  may  be  of  the  last  importance, 
for  they  more  or  less  determine  the  physician's  practice,  and 
have,  therefore,  a  direct  bearing  upon  the  lives  committed  to  his 
care. 

On  hardly  any  point  of  medical  theory,  and  the  practice 
flowing  from  it,  has  this  division  of  opinion  been  more  distinct 
than  on  the  question  of  typhoid  fever.  The  pith  of  the  con- 
troversy is  this :  Can  typhoid  fever  be  generated  anew  ?  Is  it 
produced  by  the  decomposition  and  putrefaction  of  animal  and 
vegetable  substances,  or  must  the  matter  producing  it  have  had 
previous  contact  with  an  infected  body  ?  In  other  words,  for  every 
new  case  of  typhoid  fever  may  we  with  certainty  infer  a  pre- 
existing case,  of  which  the  new  one  is  merely  the  propagation  or 
continuation  ;  or  are  we  entitled  to  conclude  that  organic  matter, 
which  has  never  been  in  contact  with  a  typhoid  patient,  is,  in 
virtue  of  its  own  decomposition,  capable  of  starting  the  fever 
anew?  When  we  consider  that  this  pest  sends  15,000  of  the 
inhabitants  of  these  islands  yearly  to  the  grave,  and  causes 
150,000  to  pass  through  its  protracted  miseries,  the  question 
here  stated  assumes  the  very  gravest  importance,  because  our 
relation  to  it  must  determine  our  mode  of  attack  upon  this  enemy 
of  mankind. 


684  LETTER   TO   THE    '  TIMES. 

The  position  taken  by  Dr.  Budd  in  reference  to  this  ques- 
tion, is  one  which  will  render  his  name  memorable  in  the  history 
of  medicine.  In  the  w<  rk  before  us  he  seeks  to  prove  that  the 
first  of  the  positions  just  laid  down  is  the  true  position;  that 
there  is  no  such  thing  as  the  spontaneous  generation  of  typhoid 
fever  ;  that  the  malady  is  propagated,  as  surely  as  smallpox  is 
propagated  through  a  special  virus,  by  contagion.  He  begins  by 
developing  his  evidence  on  this  head  ;  he  then  fixes  the  principal 
seat  of  the  contagious  matter  in  the  intestine  ;  he  examines  the 
nature  of  the  intestinal  affection,  the  relation  of  typhoid  fever  to 
defective  sewerage,  the  character  of  the  contagious  agent,  the 
employment  of  disinfectants  and  disinfection.  He  discusses  the 
so-called  '  pythoaenic' or  putrescent  theory,  and  winds  up  with 
some  remarks  on  the  spontaneous  origin  of  typhoid  fever.  The 
book,  from  beginning  to  end,  is  one  comprehensive  argument, 
with  rt  ference  to  which  it  may  be  said  that  the  facts  alleged  are 
of  the  most  conclusive  character,  while  the  logic  which  binds 
them  together  is,  as  far  as  I  can  see,  simply  irresistible. 

This  is  a  question  which  is  sure  to  occupy  the  attention  of 
legislators  as  well  as  of  physicians,  and  it  is  therefore  desirable 
to  place  it  in  the  clearest  untechnical  light.  Dr.  Budd  takes  his 
reader  to  the  village  of  North  Tawton,  where  he  was  himself 
born  and  brought  up,  and  every  inhabitant  of  which  was  per- 
sonally known  to  him.  In  the  village  there  was  no  general 
system  of  sewers.  Round  the  cottages  of  those  who  earned  their 
bread  with  their  hands,  and  who  formed  the  great  bulk  of  the 
population,  were  collected  various  offensive  matters.  Each 
cottage,  or  group  of  three  or  four  cottages,  had  a  common  privy, 
to  which  a  simple  excavation  in  the  ground  served  as  a  cesspool. 
In  many  cases,  hard  by  the  cottage  door  there  was  not  only  an 
open  privy,  but  a  dung-heap,  where  pigs  rooted  and  revelled. 
For  a  long  period  there  was  much  offensive  to  the  nose,  but  no 
fever.1  An  inquiry,  conducted  with  the  most  scrupulous  care, 
showed  that  for  fifteen  years  there  had  been  no  severe  outbreak 
of  the  disorder,  and  that  for  nearly  ten  years  there  had  been  only 
a  single  case.  '  For  the  development  of  this  fever,'  adds  Dr. 
Budd,  '  a  more  specific  element  was  needed  than  the  swine,  the 
dung-heaps,  or  the  privies  were  able  to  furnish.' 

1  This  is  the  experience  of  the  poorer  parts  of  Edinburgh.    Seep.  [21.   Ii» 
forms  manifold  the  same  experience  has  presented  itself  to  ma  in  Switzerland 


LETTER  TO   THE   *  TIMES.'  685 

That  element  at  length  came,  and  formed  a  starting-point 
from  which  its  further  progress  might  be  securely  followed.  On 
July  11,  1839,  a  case  of  typhoid  fever,  doubtless  imported  from 
without,  occurred  in  a  poor  and  crowded  dwelling,  and  before 
the  end  of  November  eighty  of  the  inhabitants  had  suffered 
from  it ;  a  proportion  about  the  s:ime  as  that  now  suffering  at 
Over  Darwen.  The  reader  will,  I  trust,  bear  strictly  in  mind 
that  the  question  now  before  us  is,  whether  typhoid  fever  is 
contagious,  and  he  is  asked  to  weigh  the  answer  which  facts 
return  to  this  question.  Two  sawyers  living  near  the  stricken 
house  at  North  Tawton,  fell  ill,  and  quitted  the  village  for  their 
own  homes  at  Marchard,  where  no  previous  case  of  typhoid 
fever  bad  been.  In  two  days  one  of  these  men  took  to  his  bed, 
and  at  the  end  of  five  weeks  he  died.  Ten  days  after  his  death, 
his  two  children  were  laid  up  with  the  fever.  The  other  sawyer 
also  took  to  his  bed,  and  when  at  the  worst  a  friend  from  a 
distance  came  to  see  him,  and  assisted  to  raise  him  in  bed  On 
the  tenth  day  after,  this  friend  was  seized  with  the  fever. 
Before  he  became  convalescent,  two  of  his  children  were  struck 
down,  and  his  brother,  who  lived  at  a  distance,  but  who  came 
to  see  him,  also  fell  a  victim.  Was  this  series  of  events  the 
result  of  chance,  or  was  it  the  work  of  contagion  ?  Let  us 
pursue  the  inquiry  further.  On  August  20,  a  Mrs.  Lee  began 
to  droop  at  North  Tawton,  and,  not  knowing  what  was  impend- 
ing, she  visited  her  brother  at  Chaffcombe,  seven  miles  off.  She 
was  smitten  with  the  fever,  and  before  she  became  convalescent, 
her  sister-in-law,  Mrs.  Sncll,  who  had  nursed  her,  was  attacked 
and  died  subsequently.  Then  came  Mr.  Snell,  then  one  of  the 
farm  apprentices,  then  a  day-labourer,  then  a  Miss  Snell,  who 
had  come  to  take  charge  of  the  house  after  Mrs.  Snell's  death ; 
ayid,  finally,  a  group  consisting  of  a  servant  man,  a  servant  girl, 
and  another  young  person  who  had  acted  as  nurse. 

The  case  here  submitted  to  the  reader  is  not  one  of  meiical 
practice,  but  of  common  evidence,  which  does  not  even  require  a 
trained  scientific  mind  to  weigh  it.  Let  us  proceed.  A  boy 
who  had  been  smitten  at  Chaffcombe  went  to  his  mother's 
cottage  between  Bow  and  North  Tawton.  Before  he  recovered, 
Ins  mother,  who  had  nursed  him,  sickened  and  died.  Two 
children  of  the  family  next  door  were  next  attacked,  then  the 
sister  of  the  boy  who  had  carried  the  infection  from  ChafFcombe. 


586  LETTER   TO   THE   'TIMES.' 

She,  in  her  turn,  removed  to  another  place,  and  became  a  new 
focus  for  the  propagation  of  the  disease.  Again,  to  lighten  the 
list  of  invalids,  a  girl  named  Mary  Gibbings  was  sent  from 
Chaffcombe  to  her  home  at  Loosebeare,  four  miles  off.  Here  she 
lay  ill  for  several  weeks.  Before  she  recovered,  her  father  was 
seized.  A  farmer  who  lived  across  the  road,  and  who  visited 
Gibbings,  was  next  struck  down.  His  case  was  followed  by 
others  under  the  same  roof;  and  the  fever,  spreading  from  this 
to  other  houses,  became  the  centre  of  an  epidemic  which  gra- 
dually extended  to  the  whole  hamlet. 

At  the  same  time,  scattered  over  the  country  side,  were  some 
twenty  or  thirty  other  hamlets,  in  each  of  which  were  the  usual 
manure  yard,  the  inevitable  pigsty,  and  the  same  primitive  ac- 
commodation for  human  needs.  '  The  same  sun  shone  upon  all 
alike  through  month  after  month  of  the  same  fine,  dry,  autumnal 
weather.  From  the  soil  of  all  these  hamlets  human  and  other 
exuvia  exhaled  into  the  air  the  same  putrescent  compounds  in 
about  equal  abundance.  In  some  of  them,  indeed,  to  speak  the 
exact  truth,  these  compounds,  if  the  nose  might  be  trusted — and 
in  this  matter  there  is  no  better  witness — were  much  more  ripe. 
And  yet,  while  at  Loosebeare  a  large  proportion  of  the  inhabit- 
ants were  lying  prostrate  with  fever,  in  not  one  out  of  the  twenty 
or  thirty  simila;  hamlets  was  there  a  single  case.'  '  There  is  no 
confusion  of  data  here ;  no  blur  or  indistinctness  in  the  observer's 
vision,  no  flaw,  as  far  as  I  can  see,  in  his  reasoning.  He  follows 
the  morbific  agent  from  place  to  place,  sees  it  planted,  developed, 
shedding  its  seeds,  producing  new  crops ;  growing  up  where  it 
is  sown,  and  there  only.  Ashpits  fail  to  develop  it ;  putrescence 
fails  to  develop  it ;  stench  fails  to  develop  it ;  even  the  open 
privy  is  powerless  as  long  as  it  is  kept  free  from  the  discharges 
of  those  already  attacked.  The  case  of  North  Taw  ton  is  typical; 
numerous  other  cases  equally  conclusive  are  adduced — among 
them  the  foul  condition  of  the  Thames  in  the  hot  weather  of 
1858  and  1859,  when  stench  for  the  first  time  '  rose  to  the  height 
of  an  historic  event ;  '  and  when,  nevertheless,  London,  even 
along  the  river,  enjoyed  a  singular  immunity  from  lever.  It  is, 

1  With  such  evidence  as  this  before  me,  corroborated  as  it  is  in  the 
most  diversified  manner  by  my  own  experience,  I  cannot  accept  for  my 
guidance  either  the  knowledge  or  the  scientific  competence  of  some  of  those 
T» -ho  have  made  this  letter  the  subject  of  criticism. 


LETTER   TO   THE   *  TIMES.'  687 

I  think,  impossible  for  any  intelligent  reader,  and  I  should  say 
certainly  impossible  for  any  man  trained  to  scientific  reasoning, 
to  quit  Dr.  Budd's  volume  without  closing  with  his  conclusion, 
that  the  living  human  body  is  the  soil  in  which  the  specific  poison 
of  typhoid  ftver  breeds  and  multiplies. 

What  is  the  seat  of  the  poison?  Dr.  Budd  is  too  cautious 
to  shut  out  the  possibility  of  infection  by  any  of  the  emanations 
from  a  person  suffering  from  the  disease.  But  its  special  and 
almost  exclusive  locus  is  the  diseased  intestine.  He  gives 
drawings  and  photographs  of  the  bowel  at  various  stages  of  the 
disease;  and  it  is  hardly  possible  to  look  on  these  without  coming 
to  the  conclusion  that  the  whole  interior  surface  of  the  bowels 
is  the  seat  of  an  eruption.  The  pustules  or  protuberant  patches, 
called  '  Peyer's  patches,'  thicken  and  stand  out  in  relief  from  the 
surface  of  the  gut.  They  feel,  to  use  the  words  of  Chomel,  as  if 
a  solid  and  elastic  substance  had  been  inserted  between  the 
coats  of  the  intestine,  while,  when  a  patch  is  cut  through,  irs 
texture  is  seen  to  be  occupied  by  a  yellowish-white  cheese-like 
matter.  '  This  is  the  peculiar  "  typhoid  matter  "  whose  presence 
is  typical  of  the  disease,  and  whose  formation  and  elimination 
constitute  the  essence  of  the  intestinal  process.'  Louis  has  made 
careful  observations  as  to  the  duration  of  the  alvine  discharge 
which  accompanies  typhoid  fever,  and  finds  it  to  be  in  mild 
cases  15,  and  in  severe  cases  25  daj-s.  For  this  period,  there- 
fore, every  individual  smitten  at  Over  Darwen  has  been  flooding 
the  undrained  ground  with  the  poison  of  this  contagious  fever. 
It  reaches  the  drinking  water ;  it  partially  dries  and  floats  in  the 
air  ;  it  rises  mechanically  with  the  gas-bubbles  issuing  from  cess- 
pools, and  thus  the  pestilence  wraps  like  an  atmosphere  the  entire 
community. 

How  could  a  disease  whose  characteristics  are  so  severely 
demonstrable  have  ever  been  imagined  to  be  non-contagious  ? 
How  could  such  a  doctrine  be  followed  out,  as  it  has  been,  to 
the  destruction  of  human  life?  Mainly  because  practice  in 
cities,  where  the  greatest  medical  authorities  reside,  was  directly 
calculated  to  throw  the  physician  off  the  scent.  The  seat  of  the 
disease  being  the  intestine,  with  well-appointed  water-closets 
it  is  not  in  the  sick-room  that  the  mischief  is  done,  but  often  at 
a  distance  from  the  sick-room,  through  the  agency  of  the  sewer, 
which  Budd  graphically  describes  as  '  a  direct  continuation  of 


688  LETTER   TO   THE   *  TIMES.' 

the  diseased  intestine.1  Hence  the  mystic  power  of  '  sewer-gas. 
Hence  the  inability  of  the  metropolitan  practitioner  to  trace  the 
disease  to  its  origin.  Hence  the  immunity  of  undrained  country 
villages  ax  long  as  the  specific  poison  keeps  away  ;  and  hence  also 
the  localised  ravages  of  the  disease  in  such  villages  as  soon  as  it 
appears. 

Were  it  not  that  I  have  already  drawn  far  too  heavily  upon 
your  space,  I  might  enlarge  upon  these  subjects.  I  will  limit 
myself  to  one  more  point  of  commanding  interest.  What  is  the 
nature  of  the  typhoid  poison  ?  The  '  yellow  typhoid  matter,' 
already  referred  to,  Budd  describes  as  made  up  of  nucleated 
cells.  The  term  'germ-theory'  does  not,  to  my  knowledge, 
occur  once  in  the  volume,  possibly  because  of  the  opposition  and 
ridicule  '  which  that  theory  encountered  in  the  English  Medical 
Press.  Over  and  over  again  Budd  speaks  of  '  germs ;  '  but  it 
might  be  imagined  that  he  used  the  word  figuratively.  Those 
who  knew  him,  however,  were  well  aware  that  this  was  not  the 
case ;  and  in  the  early  part  of  the  present  volume,  after  describ- 
ing the  calamities  incident  to  typhoid  fever,  he  remarks:  'It 
is  humiliating  that  issues  such  as  these  should  be  contingent 
on  the  powers  of  an  agent  so  low  in  the  scale  of  being  that  the 
mildew  which  springs  on  decaying  wood  must  be  considered 
high  in  comparison.'  Four  or  five  years  ago,  I,  an  outsider, 
ventured  upon  this  ground  of  medical  theory,  for  it  involved  no 
knowledge  of  medical  practice,  but  simply  a  capacity  to  weigh 
evidence ;  and  the  evidence  that  epidemic  diseases  were  parasitic 
appeared  to  me  very  strong.  On  June  9,  1871,  I  ventured  to 
express  myself  thus:  'With  their  respective  viruses  you  may 
plant  typhoid  fever,  scarlatina,  or  smallpox.  What  are  the 
crops  that  arise  from  this  husbandry  ?  As  surely  as  a  thistle 
rises  from  a  thistle-seed,  as  surely  as  the  fig  comes  from  the  fig, 
the.  grape  from  the  grape,  and  the  thorn  from  the  thorn,  so 
surely  does  the  typhoid  virus  increase  and  multiply  into  typhoid 
fever,  the  scarlatina  virus  into  scarlatina,  the  smallpox  virus 
into  smallpox.  What  is  the  conclusion  that  suggests  itself  here  ? 
It  is  this :  that  the  thing  which  we  vaguely  call  a  virus  is  to 
all  intents  and  purposes  a  seed]  that,  excluding  the  notion  of 
vitality,  in  the  whole  range  of  chemical  science  you  cannot  point 

1  Now  considerably  abated  [1876]. 


LETTER  TO   THE    'TIMES.'  689 

to  an  action  which  illustrates  this  perfect  parallelism  with  the 
phenomena  of  life — this  demonstrated  power  of  self-multiplic;ition 
and  reproduction.' l  It  was  the  clear  and  powerful  writings  of 
William  Budd,  joined  to  those  of  the  illustrious  Pasteur,  that 
won  me  to  these  views.  It  is  partly  with  a  view  of  stamping 
at  a  receptive  moment  salutary  truths  upon  the  public  mind,  but 
partly,  also,  through  the  desire  of  rendering  justice  to  a  noble 
intellect,  which  has  been  literally  sacrificed  to  the  public  good, 
that  I  draw  attention,  not  only  to  the  masterly  combination  of 
observation  and  inference  exhibited  from  beginning  to  end  of 
Dr.  Budd's  volume,  but  also  to  the  crowning  fact,  already  pub- 
lished in  the  medical  journals,  and  to  which  my  attention  was 
first  drawn  by  my  eminent  friend  Mr  Simon,  that  Dr.  Klein 
has  recently  discovered  the  very  organism  which  lies  at  the  root 
of  all  the  mischief,  and  to  the  destruction  of  which  medical  and 
sanitary  skill  will  henceforth  be  directed.8 
I  am,  Sir, 

Your  obedient  servant, 

JOHN  TYNDALL. 

KOTAL  INSTITUTION  :  Nov.  6. 


1  It  was  the  considerations  here  mentioned  that  swayed  me  at  the  outset ; 
it  is  they  that  most  powerfully  influence  my  convictions  still.  And  they 
•would  remain  if  the  causal  relation  between  recently  discovered  organisms 
and  epidemic  disease  were  disproved  to-morrow. — J.  T.,  March  1876. 

8  Dr.  Murchison  gave  this  brief  reference  to  Dr.  Klein  considerable 
prominence  in  his  remarks  before  the  Pathological  Society  on  May  4,  1875. 
He  did  not  grapple  with  the  arguments  of  Dr.  Budd,  nor  attempt  to  show 
why,  when  every  condition  laid  down  by  himself  for  the  production  of 
typhoid  fever  is  present,  the  fever  fails  to  be  produced.  See  p.  [35. 


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modest  preface.  The  result  is  the  appearance  of  a  collection  of  facts  which  will  be  i 
real  boon  to  the  student  of  Comparative  Psychology  for  this  is  the  first  attempt  to 
present  systematically  well-assured  observations  on  the  mental  life  of  animais."—  Sat- 
urday Rcvitw. 

"The  author  believes  himself,  not  without  ample  cause,  to  have  completely  bridged 
the  supposed  gap  between  instinct  and  reason  by  the  authentic  proofs  here  mar- 
shaled of  remarkable  intelligence  in  some  of  the  higher  animals.  It  is  the  seemingly 
conclusive  evidence  of  reasoning  powers  furnished  by  the  adaptation  of  means  to  end's 
in  cases  which  can  not  be  explained  on  the  theory  of  inherited  aptitude  or  habit." — 
New  York  6'wn. 

THE  SCIENCE  OF  POLITICS.    By  SHELDON  AMOS,  M.  A.,  author  of "  The 
Science  of  Law,"  etc.    12mo.     Cloth,  $1.75. 

"  To  the  political  student  and  the  practical  statesman  it  ought  to  be  of  great  value." 
— New  York  H^ra'.d. 

"  The  author  traces  the  subject  from  Plato  and  Aristotle  in  Greece,  and  Cicero  in 
Rome,  to  the  modern  schools  in  the  English  field,  not  slighting  the  teachings  of  the 
American  Revolution  or  the  lessons  of  the  French  Revolution  of  1798.  Forms  of  gov- 
ernment, political  terms,  the  relation  of  law.  written  and  unwritten,  to  the  subject,  a 
codification  from  Justinian  to  Napoleon  in  France  and  Field  in  America,  are  treated 
as  parts  of  the  subject  in  hand  Necessarily  the  subjects  of  executive  and  legislative 
authority,  police,  liquor,  and  land  laws  are  considered,  and  the  question  ever  growing 
in  importance  in  all  countries,  the  relations  of  corporations  to  the  state." — A'ew  York 
Observer.  

New  York :  D.  APPLETON  &  CO.,  1,  3,  &  5  Bond  Street. 


Scientific  Publications. 


ANTS,  BEES,  AND  WASPS.  A  Record  of  Observations  on  the  Habits  of  tha 
Social  Hytnenoptera.  By  Sir  JOHN  LUBBOCK,  Bart.,  M.  P.,  F.  R.  8 ,  etc.,  author 
of  "  Origin  of  Civilization,  and  the  Primitive  Condition  of  Man, '  etc.,  etc.  With 
Colored  Plates.  12mo,  cloth,  $2.00. 

"This  volume  contains  the  record  of  various  experiments  made  with  ants,  bees,  and 
wasps  during  the  last  ten  years,  with  a  view  to  test  their  mental  condition  and  powers 
of  sense.  The  principal  point  in  wnich  :?ir  John's  mode  of  experiment  differs  from 
those  of  Huber,  Forel,  McCook,  and  others,  is  that  he  has  carefully  watched  and 
marked  particular  insects,  and  has  had  their  nests  under  observation  for  long  periods 
—one  of  his  ants'  nests  having  been  under  constant  inspection  ever  since  li>74.  His 
observations  are  made  principally  upon  ants  because  they  show  more  power  and  flexi- 
bilii.y  of  mind ;  and  the  value  of  his  studies  is  that  they  belong  to  the  department  of 
original  research." 

"  We  have  no  hesitation  In  saying  that  the  author  has  presented  us  with  the  most 
valuable  series  of  observations  on  a  special  subject  that  has  ever  been  produced,  churiu- 
ing-ly  written,  full  of  logical  deductions,  and,  when  we  consider  his  multitudinous  en- 
gagements, a  remarkab.e  illustration  of  economy  of  time.  As  a  contribution  to  insect 
psychology,  it  will  be  long  before  this  book  nnds  a  parallel.1'— London  AthetMum. 

DISEASES  OF  MEMORY :  An  Essay  in  the  Positive  Psychology.  By  TH, 
RIBOT,  author  of  "  Heredity,"  etc  Translated  from  the  French  by  William 
Huntington  Smith.  12mo,  cloth,  $150. 

"  M.  Ribot  reduces  diseases  of  memory  to  law,  and  his  treatise  is  of  extraor- 
dinary interest."— PliUadflphi  *  Press. 

''Not  merely  to  scientific,  but  to  all  thinking  men,  this  volume  will  prove 
intensely  interesting." — New  York  Observer. 

"M.  Ribot  has  bestowed  the  most  painstaking  attention  upon  hi«  theme, 
and  numerous  examples  of  the  conditions  cocsidered  greatly  increase  the  value 
and  interest  or  the  volume."— Philadelphia  North  American. 

"  To  the  general  reader  the  work  is  made  entertaining  by  many  illustrations 
connected  with  such  names  as  Linnaeus.  Newton,  Sir  Walter  Scott,  Horace  Yer- 
net,  Gu.siave  Dore,  and  many  others." — Harrisbwg  Telegraph. 

"The  vvho'e  pnbject  is  presented  with  a  Frenchman's  vivacity  of  style." — 
Providence  Journal. 

'•It  is  not  too  much  to  say  that  in  no  single  work  have  so  many  curious 
cisss  been  brought  together  aud  interpreted  in  a  scientific  manner."— ^Boston 
Evening  Traveller. 

MYTH  AND  SCIENCE.    By  TITO  VIGHOLT.  ;12mo,  cloth,  price,  fl.5». 

"  His  book  is  ingenious ;  .  .  .  his  theory  of  how  science  gradually  differen- 
tiated from  and  conquered  myth  is  extremely  well  wrought  out,  and  is  probably  in 
essentials  correct."— Saturday  Review. 

"The  book  is  a  strong  one,  and  far  more  interesting  to  the  general  reader  than  its 
title  jvould  indicate.  The  learning,  the  acutcncss.  the  strong  reasoning  power,  and  the 
scientific  spirit  of  the  author,  command  admiration." — New  Yurk  Christian  Advocate. 

"  An  attempt  marie,  with  much  ability  and  no  small  measure  of  success,  to  trace  the 
erigin  and  development  of  the  myth.  The  author  has  pursued  his  inquiry  with  much 
patience  and  ingenuity,  and  has  produced  a  very  readable  and  luminous  treatise."— 
Philadelphia  North  American. 

"It  is  a  curious  if  not  startling  contribution  both  to  psychology  and  to  the  early 
history  of  man's  development." — New  York  World. 


For  sale  by  all  booksellers;  or  sent  by  mail,  post-paid,  on  receipt  of  price. 
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THE  BRAIN  AND  ITS  FUNCTIONS.  By  J.  LCYS,  Physician  to  the 
Hospice  de  la  Salpetriere.  With  Illustrations.  12mo.  Cloth,  $1.50. 

"No  living  physiologist  is  better  entitled  to  speak  with  authority  upon  tho 
structure  and  function*  of  the  brain  than  l)r.  Luys.  Hi"  studies  ou  the  anatomy 
of  the  nervous  system  are  acknowledged  to  be  the  fullest  and  most  systematic 
eVi-r  undertaken.  Dr.  Luys  supports  his  conclusions  not  only  by  his  own  ana- 
tomical re -cardies,  but  also  by  many  functional  observations  of  various  oilier 
physiologist-",  including  of  course  Professor  Ferrier's  now  classical  experi- 
ments."— St.  James's  Gazette. 

"  Dr.  Luys,  at  the  head  of  the  great  French  Insane  Asylum,  is  one  of  the  most 
eminent  aiid  successful  investigators  of  cerebral  science  now  living;  and  he  has 
given  unquestionably  the  clearest  and  most  interesting  brief  account  yet  made  of 
the  structure  and  operations  of  the  brain.  We  have  been  fascinated  by  this  vol- 
ume more  than,  by  f.ny  other  treatise  we  have  yet  seen  on  the  machinery  of  sen- 
sibility and  thought ;  and  we  have  been  instructed  not  only  by  irucn  that  is  new, 
but  by  many  sagacious  practical  hints  such  as  it,  is  well  lor  everybody  to  under- 
stand."—  The  I'opular  Science  Monthly. 

THE   CONCEPTS  AND  THEORIES   OF  MODERN  PHYSICsi.    Fy 

J.  B.  STALLO.    12mo.    Cloth,  $1.75. 

"  Jnd?e  Stallo's  work  is  an  inquiry  into  the  validity  of  those  mechanical  con- 
ceptions of  the  universe  which  are  now  held  as  fundamental  in  physical  science. 
He  tak';s  up  the  bading  modern  doctrines  which  are  based  um  n  this  mechanical 
conception,  such  as  the  atomic  constitution  of  matter,  the  kinetic  theory  of  gases, 
the  conservation  of  energy,  the  nebilar  hypothesis,  and  other  views,  to  find  how 
much  stands  upon  solid  empirical  irrooncL  and  how  much  rests  upon  metaphys- 
ical speculation.  Since  the  appearance  of  Dr.  Draper's  'Religion  and  Science,' 
no  book  lias  been  published  in  the  country  calculated  to  make  so  deep  an  impres- 
sion on  thoughtful  and  elucated  readers  as  this  volume.  .  .  .  The  range  and 
miimtenes-i  oT  the  author's  learning,  the  a  utene^s  of  his  reasoning,  and  the 
singular  precision  ind  clearness  of  his  style,  are  qualities  which  very  seldom 
have  been  joinrly  exhibited  in  a  scientific  treatise.''— Kew  York  Sun. 

THE  FORMATION  OF  VEGETABLE  MOULD.  THROUGH  THE 
ACTION  OF  WORMS,  WITH  OBSERVATIONS  ON  THEIR 
HABITS.  By  CHARLES  DARWIN,  LL.  D.,  F.  R.  8.,  author  of  "  On  the 
Origin  of  Species,"  etc.,  etc.  With  Illustrations.  12mo,  cloth.  Price,  $1.50. 

"  Mr.  Darwin's  little  volume  on  the  habits  and  instincts  of  earth-worms  is  no 
lesa  marked  than  the  earlier  or  more  elaborate  efforts  of  his  genius  by  freshness 
of  observation,  unfailing  power  of  interpreting  and  correlating  facts,  and  logical 
vigor  !n  generalizing  npon  them.  The  main  purpose  of  the  work  is  to  point  out 
the  share  which  worms  have  taken  in  the  formation  of  the  layer  of  vegetable 
mould  which  covers  the  whole  surface  of  the  1-md  in  every  moderately  humid 
country.  All  lovers  of  nature  will  unite  in  thanking  Mr.  Darwin  for  the  new  and 
interesting  li  rht  he  has  thrown  upon  a  subject  PO  long  overlooked,  yet  so  full  of 
interest  and  ;nstructiou,  as  the  structure  and  the  labors  of  the  earth-worm." — 
Sat  rday  Review. 

"  Respecting  worms  as  among  the  most  useful  portions  of  animate  nature, 
Dr.  Darwin  relates,  in  thi«  remarkable  book.  tl>eir  structure  and  habits,  the  psrt 
they  hrtve  played  in  the  burial  of  ancient  buildings  and  the  denudation  of  the 
land,  in  the  disintegration  of  rocks,  the  preparation  of  soil  for  the  growth  of 
plants,  and  in  the  natural  history  of  the  world." — Boston  Advertiser. 

D,  APPLETON  &  CO.,  Publishers, 

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SUICIDE  :  An  Essay  in  Comparative  Moral  Statistic*.  By  HKNET  MOFBELLI,  Pro- 
fessor  of  Psychological  Medicine  in  KoyalUniversity,  Turin,  limo,  doth,  fl.f 0. 
44  Suicide  "  is  a  scientific  inquiry,  on  the  basis  of  the  statistical  method,  Into  the  laws 
of  suicidal  phenomena.  Dealing  with  the  su  ject  as  a  branch  of  social  science,  it  con- 
siders the  increase  of  suicide  in  different  countries,  and  the  comparison  of  nations, 
races,  and  periods  in  its  manifestation.  T  he  influences  ot  age,  sex.  constitution,  cli- 
mate, season,  occupation,  religion,  prevailing  ideas,  the  elements  of  character,  and  the 
ftend  -ncies  of  civilization,  are  comprehensively  analyzed  in  their  learing  upon  the  pro- 
pensity to  sell-destruction.  Professor  Morselli  is  an  eminent  European  authority  on 
this  subject.  It  is  accompanied  by  colored  maps  illustrating  pictorially  the  results  of 
statistical  inquiries. 

VOLCANOES  :  What  they  Are  and  what  they  Teach.    By  J.  W.  JTTDD, 

Professor  of  Geology  in  the  Koyal  bchool  of  Mines  (London).  With  Ninety -six 
Illustrations.  12mo.  Cloth,  $-J.O<). 

44  Tn  no  field  has  modern  research  been  more  fruitful  than  in  that  of  which  Professor 
Judd  gives  a  popular  account  in  the  present  volume.  The  great  lines  of  dynamical, 
geo.'oirical,  and  meteorological  inquiry  converge  upon  the  grand  problem  ol  the  interior 
constitution  of  the  earth,  and  the  vast  influence  of  tubterrancan  agencies  .  .  .  His 
book  is  very  far  from  being  a  mere  dry  description  of  volcanoes  and  iheir  eruptions  ;  it 
is  rather  a  presentation  of  the  terrestrial  facts  and  laws  with  which  volcanic  phenomena 
are  associated."  —Popular  Science  Month'y. 

"  The  volume  before  us  is  one  of  the  pleasantest  science  manuals  we  have  read  for 
gome  time."— Athenaeum. 

41  Mr.  Ju'ld's  summary  is  so  full  and  so  concise  that  it  is  almost  impossible  to  give 
a  fair  idea  in  a  short  review."— Pall  Mall  Gazette. 

THE  SUN.  By  C.  A.  Yor/^o.  Ph.  D.,  LL.  D.,  Professor  of  A  stronomy  in  the  College 
of  New  Jersey.  With  numerous  Illustrations.  12mo.  Cloth,  s|  2.00. 

41  Professor  Young  is  an  authority  on  •  The  Sun.'  and  writes  from  intimate  knowl- 
edge. He  has  studied  that  great  luminary  all  his  life,  invented  and  in  proved  instru- 
ments for  bserving  it.  gone  to  all  quarters  of  the  world  in  search  of  tt-e  test  places 
and  opportunities  to  watch  it,  and  has  contributed  important  discoveries  that  have 
extendel  our  knowledge  ot  it. 

44  It  would  take  a  cyclopttdia  to  represent  all  that  has  been  done  toward  clearing  up 
the  solar  mysteries.  Professor  Young  has  summarized  the  information,  and  presente  1 
it  in  a  form  completely  available  for  general  readers.  There  is  no  rhetoric  in  his  book ; 
he  trusts  the  grandeur  of  his  theme  to  'iindle  interest  and  impress  the  feelings.  His 
statements  are  plain,  direct,  clear,  and  condensed,  though  ample  enough  for  his  purpo.^e. 
and  the  substance  of  what  is  generally  wanted  will  be  found  accurate.y  given  in  his 
pages." — Popular  Science  Monthly. 

IIXUSIONS  :  A  Psychological  Study.  By  JAMES  SCLLT,  author  of"  Sensa- 
tion and  Intuition,"  etc.  12mo.  Cioth.  $1.50. 

This  volume  takes  a  wide  survey  of  the  field  of  error,  embracing  in  its  view  not  only 
the  illusions  commonly  regarded  as  of  the  nature  of  mental  aberrations  or  hallucina- 
tions, but  also  other  illusions  arising  from  that  capacity  for  error  which  belongs  essen- 
tially to  rational  human  nature  T-e  author  has  endeavored  to  keep  to  a  strictly  scien- 
tific treatment— that  is  to  say.  the  description  and  classification  of  acknowledged  errors, 
and  the  exposition  ot  them  by  a  reference  to  their  psychical  ard  physical  conditions 

"  This  is  not  a  technical  work,  but  one  of  wide  popular  interest,  in  the  principles  and 
results  of  which  every  one  is  concerned.  The  illusions  of  perception  of  the  sense's  and 
of  dreams  are  first  considered,  and  then  the  author  passes  to  the  illusions  of  introspec- 
tion, errors  of  insight,  illusions  of  memory,  and  illusions  of  belief.  The  work  is  a  hole- 
worthy  contribution  to  the  original  progress  of  thought,  and  may  b?  relied  upon  as 
representing  the  present  state  of  knowledge  on  the  important  subject  to  which  it  is 
devoted." — PoptUar  Science  Monthly. 

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GENERAL,  PHYSIOLOGY  OF  MUSCLES  AND  NERVES.    By  Dr.  I. 

ROSENTHAL,  Professor  of  Physiology  at  the  University  of  Erlangen.  With 
seventy-five  Woodcuts.  ("  International  Scientific  Series.")  12mo,  cloth, 
$1.50. 

"  Th?  attempt  at  a  connected  account  of  the  general  physiology  of  muscles 
hnd  nerves  is,  as  far  as  I  know,  the  first  of  its  kind.  The  general  data  lor  this 
branch  of  science  hare  been  gained  ouly  within  the  past  thirty  years.11— Extract 
from  Preface. 

SIGHT  :  An  Exposition  of  the  Principles  of  Monocular  and  Binocular  Vision 
By  JOSEPH  LE  CONTE,  LL. I).,  author  of  "  Elements  of  Geology";  "Re- 
ligion and  Science  "  ;  and  Professor  of  Geology  and  Natural  History  in  the 
University  of  California.  With  numerous  Illustrations.  I2mo,  cloth,  $1.CO. 

"  It  is  pleasant  to  find  an  American  book  whirh  can  rank  with  the  very  b^st 
of  foreign  works  on  this  subject.  Professor  Le  Conte  has  long-  been  known  as 
an  original  investigator  in  this  department;  all  that  he  gives  us  is  treated  with 
a  master-hand."—  The  Nation. 

ANIMAL  LIFE,  as  affected  liy  the  Natural  Conditious  of  Existence.  By 
KABL  SEMPER,  Professor  of  the  University  of  Wiirzburg.  With  2  Maps 
and  106  Woodcuts,  and  Index.  12mo,  cloth,  $2.00. 

"  This  is  in  many  respects  one  of  the  most  interesting  contributions  to 
zoological  literature  which  has  appeared  for  some  time."— Nature. 

THE  ATOMIC  THEORY.  By  AD.  WTJRTZ.  Membre  de  Hn«titut ;  Doyen 
Honoraire  de  la  Fa^ulte  de  Medecine  ;  Profespeura  la  Facnlte  des  Sciences 
de  Paris.  Translated  by  E.  CLEMINSHAW,  M.  A.,  P.  C.  8.,  F.  I.  C.,  Assist- 
ant Master  at  Sherborne  School.  12mo,  cloth,  $1.50. 

•  There  was  need  for  a  book  like  this,  which  discusses  the  atomic  theory  both 
Ls  historic  evolution  and  in  its  present  form.    And  perhaps  no  man  of  this 
a>_re  could  have  been  selected  so  able  to  perform  the  task  in  a  masterly  way  as 


in  its  historic  evolution  and  in  its  present  form.  And  perhaps  no  man  of  this 
a>_re  could  have  been  selected  so  able  to  perform  the  task  in  a  masterly  way  as 
the  illustrious  French  chemist.  Adolph  Wurtz.  It  if  impossible  to  convey  to  the 


rea-ler,  in  a  notice  like  this,  any  adequate  idea  of  the  scope,  lucid  instructiveness. 
and  scientific  interest  of  Professor  Wnrtz's  bo(  k.  The  modern  problems  of 
chi-mistry,  which  are  commonly  so  obscure  from  imperfect,  exposition,  are  here 
made  wonderfully  clear  and  attractive."—  The  Popular  Science  Monthly. 

THE  CRAYFISH.    An  Introduction  to  the  Study  of  ZoOlogy.    By  Professor 
T.  H.  HUXLEY,  F.  R.  8.    With  82  Illustrations.    12mo,  cloth,  $1.75. 

"  Whoever  will  follow  these  pages,  crayfish  in  hand,  and  will  try  to  verify  for 
Jiimself  the  statements  which  they  contain,  will  find  himself  brought  face  to  face 
with  all  the  ureat  zoological  questions  which  excite  so  lively  an  interest  at  the 
present  day." 

'•  The  reader  of  this  valuable  monograph  wiU  lay  it  down  with  a  feelinar  of 
wonder  at  the  amount  and  vnriaty  of  matter  which  has  been  got  out  of  BO  aeem- 
icgly  slight  and  unpretending  a  subject."— Saturday  Review. 

D.  APPLETON   &  CO.,  Publishers, 

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THE   HUMAN  SPECIES.    By  A.  DE  QUATREFAGES,  Professor  of  Anthro- 
pology in  the  Museum  of  Natural  History,  Paris.    12mo,  cloth,  *2.00. 
The  work  treats  of  Hie  unity,  origin,  antiquity,  and  original  localization  of 
the  human  snecies.  peopling  of  the  globe,  acclimatlzafon,  primitive  man.  forma- 
tion of  the  human  races,  fossil  human  races,  present  human  races,  and  the  physi- 
tal  and  psychological  characters  of  mankind. 

STUDENTS'  TEXT-BOOK  OF  COLOR ;  or,  MODERN  CHROMA T- 
ICS.  With  Applications  to  Art  and  Industry.  With  130  Origii  al  Illus- 
trations, and  Frontispiece  in  Colors.  By  OGDEN  N  ROOD,  Professor  of 
Physics  in  Columbia  College.  12mo,  cloth,  $2.00. 

"In  this  interesting  book  Professor  Rood,  who.  as  a  distinguished  Professor 
of  Physics  in  Columbia  College.  United  States,  must  be  accepted  as  a  competent 
authority  on  the  branch  of  science  of  which  he  treats,  deal-  briefly  and  succinctly 
with  what  may  be  termed  the  scientifl-  rationales  his  subject".  But  the  chief 
value  of  his  work  is  to  be  attributed  to  the  fact  that  he  is  himself  an  accom- 
plished arti-t  as  well  as  an  authoritative  expounder  of  science."— Edinburgh 
Rev&w,  October,  Ib79,  in  an  en  tide  on  "  The  Philosophy  of  Color." 

EDUCATION  AS  A  SCIENCE.  By  ALEXANDER  BAIN,  LL.  D.  12mo,  cloth, 
$1.75. 

"  This  work  must  be  pronounced  the  most  remarkable  fli=cnssion  of  educa- 
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bespeak  for  it  the  widest  circulation  and  the  most  earnest  attention.  It  should 
be  in  the  hands  of  every  school-teacher  and  friend  of  education  throughout  the 
land.11— New  York  Sun. 

A.  HISTORY  OF  THE  GROWTH  OF  THE  STEAM-ENGINE.    By 

ROBERT  H.  THUESTON,  A.  M.,  C.  E..  Professor  of  Mechanical  Engineering 
in  the  Stevens  Institute  of  Technology,  Hobokfin,  N.  J.,  etc.  With  163 
Illnst  rat  ions,  including  15  Portraits.  12mo,  cloth,  $2.50. 

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/olkwed  by  interesting  biographies  of  the  more  important  inventors.  If.  as  \s 
contended,  the  steam  engine  is  the  most  important  physical  agent  in  civilizing 
the  world,  its  history  is  a  desideratum,  and  the  readers  of  the  present  work  will 
agree  that  it  could  nave  a  no  more  amusing  and  intelligent  historian  than  our 
author." — Boston  Gazette. 

STUDIES  IN  SPECTRUM  ANALYSIS.  By  J.  NOHMAN  LOCKTER.  F.  R.  8  , 
Correspondent  of  the  Institute  of  France,  etc.  With  60  Illustrations.  12mo, 
cloth,  $2.50. 

"The  study  of  spectrum  analvsis  is  one  fraught  with  a  peculiar  fascination, 
and  some  of  the  author's  experiments  are  exceedingly  picturesque  in  their  re- 
sults. They  are  so  lucidly  described,  too  that  the  reader  keeps  on.  from  page 
to  pase.  nevsr  flaifiiin^  in  interest  in  the  natter  befor--  him,  nor  putting  down 
U»e  book  until  the  last  page  is  reached."—  New  York  Evening  Excess. 

D.  APPLETON  &  CO.,  Publishers, 

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SCIENTIFIC  LECTURES  AND  ESSAYS. 
Popular  Lectures  on  Scientific  Subjects.    By  H. 

HELMHOLTZ,  Professor  of  Physics  in  the  University  of  Berlin.  First 
Series.  Translated  by  E.  ATKINSON,  Ph.  D.,  F.  C.  S.  With  an  Intro- 
duction  by  Professor  TYNDALL.  With  51  Illustrations.  12uio. 
Cloth,  $2.00. 

CONTENTS.-?*  the  Relation  of  Natural  Science  to  Science  in  General.- 
pn  Goethe's  Scientific  Res.-arches.-On  the  Physiological  Causes  of  IIarmo,,y  in 
Music.— Ice  and  Glaciers.— Interaction  of  the  Katural  Forces.— The  Recent  Prog- 
ram ot  tne  rheory  ot  Vision.— Tue  Conservation  of  Force.— Aim  and  Progress 

Popular  Lectures  on  Scientific  Subjects.    By  H. 

HELMHOLTZ.     Second  Series.     12mo.     Cloth,  $1.50. 
CONTENTS.— Gustav  Magnu?.— In  Memoriam.— The  Origin  and  Significance 
of  Geometrical  Axioms.— Relation  of  Optics  to  Painting. -Origin  of  the  "Planetary 
System.— On  '1  bought  in  Medicine.— Academic  Freedom  in  German  Universities. 

"  Professor  Helmholtz's  second  series  of 'Popular  Lectures  on  Scientific  Sub- 
jects' torrns  a  volume  of  singular  interest  and  value.  He  who  anticipate!'  a  dry 
record  of  fact*  or  a  sequence  of  immature  eeneraliznticn  will  find  himself  happily 
mistaken.  In  style  and  method  these  discourses'  are  nrodels  of  excellence,  and, 
eince  they  come  from  a  man  whose  learning  ai:ri  (minority  nre  beyond  dispute, 
they  may  be  accepted  as  presentmsr  the  conclusions  ot  the  beet  thought  of  th*> 
times  in  scieu title  fields.*'— Boston  Traveler. 

Science  and  Culture,  and  other  Essays.  By  Pro- 
fessor T.  H.  HCXLEY,  F.  R.  S.  12rno.  Cloth,  $1.50. 

"Of  the  essay*  that  have  been  collected  by  Professor  Huxley  in  this  volume, 
tn«  first  tour  deal  with  some  aspect  of  education.  Most  of  the  remainder  are  ex- 
positions  of  the  results-  of  biological  research,  and.  at  the  same  time,  illustrations 
of  the  history  of  scientific  ideas.  Some  of  these  are  among  the  most  intereslir.g 
of  Prolessor  Huxley's  contributions  to  the  literature  oi  science." — London  Acad- 
emy. 

"It  is  refreshing  to  be  brought  into  converge  with  one  of  the  most  vigorous 
and  acute  thinkers  of  onr  time,  who  has  the  power  of  putting  his  thoughts  into 
language  so  clear  and  forcible."— London  Spectator. 

Scientific  Culture,  and  other  Essays.    By  JOSIAH 

PARSONS  COOKE,  Professor  of  Chemistry  and  Mineralogy  in  Harvard 

College.     12mo.     Cloth,  $1.00. 

These  e«says  are  an  outcome  of  a  somewhat  laree  experience  in  teaching 
physical  science  to  college  students.  Cambridge.  Massachusetts,  early  set  the 
example  of  makins  the  student's  own  observatiors  in  tlie  laboratory  or  csbii  et 
the  basis  of  all  teaching,  either  in  experimental  or  natural  history  ecierce  :  in  d 
jhis  example  has  been  gene-ally  followed.  "But  in  most  centers  of  ef!nciiti<  n." 
writes  Professor  Cooke.  "the  eld  traditions  so  tar  survive  that  the  great  end  of 
fcientific  culture  is  lost  in  attemptine  to  conform  even  laboratory  instruction  10 
the  old  academic  methods  of  recitations  and  examinations.  To  point  out  ibis 
error,  and  to  claim  for  science -teaching  its  appropriate  methods,  was  one  object 
of  writing  these  essays." 

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DARWINISM  STATED  BY  DARWIN 
HIMSELF:  CHARACTERISTIC  PASSAGES 
FROM  THE  WRITINGS  OF  CHARLES  DAR- 
WIN. 

SELECTED  AND  ARRANGED  BY  PROFESSOR  NATHAN   SHEPPARD. 
12mo.     Cloth,  $1.50. 


By  means  of  a  systematic  selection  of  passages  from  the  various  writ- 
ings of  Charles  Darwin,  the  reader  of  this  volume  is  enabled  to  grasp 
readily  the  scope  of  Darwin's  argument  as  to  the  origin  and  evolution  of 
species. 

"The  general  reader  may  well  be  thankful  for  this  compilation,  and  the 
greate-t  physicist  in  the  world  is,  after  all,  nothing  more  than  a  general  reader 
in  paleontology  and  the  theory  of  groups."— Science. 

"  He  has  succeeded  far  better  than  many  persons  familiar  with  Darwin's 
work?,  would  have  thought  possible.  Tne  book  is,  indeed,  in  all  respect?  a 
notable  example  of  clever  and  conscientious  ediiinir,  for  which  the  compiler  is 
entitled  to  hiirh  praise."— New  York  Commercial  Advertiser. 

'•  Mr.  Sheppard  must  be  credited  with  exemplifying  the  spirit  of  impartial 
truth-seeking  which  inspired  Darwin  himself.  From  these  condensed  results  of 
the  hard  labor  of  selection,  excision,  and  arrangement  applied  to  more  than  a 
dozen  volumes  it  is  impossible  to  draw  any  inference  respecting  the  philosophical 
opinions  of  the  compiler.  With  the  exception  of  a  brief  preface  there  is  not  a 
word  of  comment,  nor  is  there  the  faintest  indication  of  an  attempt  to  inlu.-e 
into  Darwin's  textu  meaning  not  patent  there,  by  unwarranted  sub-titles  or  head- 
lines, by  shrewd  omission,  unfair  emphasis,  or  artfal  collocation.  Mr.  Shep- 
pard has  nowhere  swerved  from  his  purpose  of  showing  in  a  ciear,  connected, 
and  very  compendious  form,  not  what  Darwin  may  have  meant  or  has  been 
charged  with  meaning,  but  what  he  actually  said."—  The  Sun. 

"  That  there  is  coming  a  time  when  Darwin's  own  Darwinism  will  be  accepted 
as  the  world's  every-day  belief,  from  pulpit  to  hut,  nobody  who  can  read  the  sisriis 
of  ths  limns  will  deny.  The  editor  quotes  in  the  beginning  some  fourteen 
eminent  religions  aut  loritias  on  the  subject.  Some  of  them  accept  his  teachings 
outright,  and  find  nothing  in  them  opposed  to  religion.  AH  speak  of  him  in  the 
highest  terms.  Darwinism,  as  popularly  understood,  however,  i*  very  different 
indeed  from  the  real  teachings  of  this  marvelous  man.  Professor  Sheppard  has 
done  well  to  here  place  in  popular  form  the  miin  points  of  the  theory,  in  extracts 
from  the  author's  own  writings."—  The  World. 

"  This  compilation  has  a  twofold  use.  of  which  the  one  is  to  form  an  introduc- 
tion to  the  study  of  Darwin's  works,  the  other  to  serve  as  a  memorandum  for 
those  who  have  read  them.  It  is  of  uniform  size  and  binding  with  the  works  of 
Darwin,  and  forms  a  useful  disrest,  and  in  some  sort  an  index  of  the  twelve 
volumes  by  the  great  naturalist."-  The  New  York  Times. 

"  Mr.  Sheppard's  plan  is  a  good  one.  He  does  not  condense  or  translate  the 
author's  language.  He  gives  us  the  languasre  itself.  It  was  a  difficult  task  to 
perform.  It  required  literary  Bkill  and  good  judgment.  Mr.  Sheppard  has  both, 
and  by  judicious  selection  and  management  he  has  given  us  the  substance  of 
Darwin's  teaching."- The  New  York  Heralt. 

"  Those  who  are  desirous  of  obtaining  a  general  idea  of  Darwin's  lino  of  argu- 
ment and  research,  and  have  not  the  means  to  obtain,  or  the  time  to  rear1  the 
numerous  volumes  In  which  they  are  fully  stnte'i.  will  find  in  this  work  an 
authentic  and  inexpensive  summary  of  his  scientific  views,  expressed  in  his 
own  language."—  The  Observer. 


New  York:  D.  APPLETON  &  CO.,  1,  3,  &  5  Bond  Street. 


UNIVERSITY  OF  CALIFORNIA  AT  LOS  ANGELES 

THE  UNIVERSITY  LIBRARY 
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